#line 1 "yu.cpp"
#line 1 "yu.cpp"
#include <bits/extc++.h>

#line 5 "Library\\config.hpp"
namespace config {
const auto start_time{std::chrono::system_clock::now()};
int64_t elapsed() {
  using namespace std::chrono;
  const auto end_time{system_clock::now()};
  return duration_cast<milliseconds>(end_time - start_time).count();
}
__attribute__((constructor)) void setup() {
  using namespace std;
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  cout << fixed << setprecision(15);
#ifdef _buffer_check
  atexit([] {
    ofstream cnsl("CON");
    char bufc;
    if (cin >> bufc)
      cnsl << "\n\033[43m\033[30mwarning: buffer not empty.\033[0m\n\n";
  });
#endif
}
unsigned cases(void), caseid = 1;
template <class C> void main() {
  for (const unsigned total = cases(); caseid <= total; ++caseid) C();
}
}  // namespace config
#line 3 "Library\\gcc_builtin.hpp"
namespace workspace {
constexpr int clz32(const uint32_t &n) noexcept { return __builtin_clz(n); }
constexpr int clz64(const uint64_t &n) noexcept { return __builtin_clzll(n); }
constexpr int ctz(const uint64_t &n) noexcept { return __builtin_ctzll(n); }
constexpr int popcnt(const uint64_t &n) noexcept {
  return __builtin_popcountll(n);
}
}  // namespace workspace
#line 2 "Library\\gcc_option.hpp"
#ifdef ONLINE_JUDGE
#pragma GCC optimize("O3")
#pragma GCC target("avx,avx2")
#pragma GCC optimize("unroll-loops")
#endif
#line 5 "Library\\utils\\binary_search.hpp"
namespace workspace {
// binary search on discrete range.
template <
    class iter_type, class pred_type,
    std::enable_if_t<
        std::is_convertible_v<std::invoke_result_t<pred_type, iter_type>, bool>,
        std::nullptr_t> = nullptr>
iter_type binary_search(iter_type ok, iter_type ng, pred_type pred) {
  assert(ok != ng);
  intmax_t dist(ng - ok);
  while (std::abs(dist) > 1) {
    iter_type mid(ok + dist / 2);
    if (pred(mid))
      ok = mid, dist -= dist / 2;
    else
      ng = mid, dist /= 2;
  }
  return ok;
}
// binary search on real numbers.
template <
    class real_type, class pred_type,
    std::enable_if_t<
        std::is_convertible_v<std::invoke_result_t<pred_type, real_type>, bool>,
        std::nullptr_t> = nullptr>
real_type binary_search(real_type ok, real_type ng, const real_type eps,
                        pred_type pred) {
  assert(ok != ng);
  while (std::abs(ok - ng) > eps) {
    real_type mid{(ok + ng) / 2};
    (pred(mid) ? ok : ng) = mid;
  }
  return ok;
}
}  // namespace workspace
#line 3 "Library\\utils\\casefmt.hpp"
namespace workspace {
std::ostream &casefmt(std::ostream &os) {
  return os << "Case #" << config::caseid << ": ";
}
}  // namespace workspace
#line 3 "Library\\utils\\chval.hpp"
namespace workspace {
template <class T, class Comp = std::less<T>>
bool chle(T &x, const T &y, Comp comp = Comp()) {
  return comp(y, x) ? x = y, true : false;
}
template <class T, class Comp = std::less<T>>
bool chge(T &x, const T &y, Comp comp = Comp()) {
  return comp(x, y) ? x = y, true : false;
}
}  // namespace workspace
#line 3 "Library\\utils\\fixed_point.hpp"
namespace workspace {
// specify the return type of lambda.
template <class lambda_type> class fixed_point {
  lambda_type func;

 public:
  fixed_point(lambda_type &&f) : func(std::move(f)) {}
  template <class... Args> auto operator()(Args &&... args) const {
    return func(*this, std::forward<Args>(args)...);
  }
};
}  // namespace workspace
#line 2 "Library\\utils\\sfinae.hpp"
#include <type_traits>
template <class type, template <class> class trait>
using enable_if_trait_type = typename std::enable_if<trait<type>::value>::type;
template <class Container>
using element_type = std::remove_const_t<std::remove_reference_t<decltype(
    *std::begin(std::declval<Container &>()))>>;
#line 7 "Library\\utils\\hash.hpp"
namespace workspace {
template <class T, class = void> struct hash : std::hash<T> {};
template <class Unique_bits_type>
struct hash<Unique_bits_type,
            enable_if_trait_type<Unique_bits_type,
                                 std::has_unique_object_representations>> {
  size_t operator()(uint64_t x) const {
    static const uint64_t m = std::random_device{}();
    x ^= x >> 23;
    // x *= 0x2127599bf4325c37ULL;
    x ^= m;
    x ^= x >> 47;
    return x - (x >> 32);
  }
};
template <class Key> size_t hash_combine(const size_t &seed, const Key &key) {
  return seed ^
         (hash<Key>()(key) + 0x9e3779b9 /* + (seed << 6) + (seed >> 2) */);
}
template <class T1, class T2> struct hash<std::pair<T1, T2>> {
  size_t operator()(const std::pair<T1, T2> &pair) const {
    return hash_combine(hash<T1>()(pair.first), pair.second);
  }
};
template <class... T> class hash<std::tuple<T...>> {
  template <class Tuple, size_t index = std::tuple_size<Tuple>::value - 1>
  struct tuple_hash {
    static uint64_t apply(const Tuple &t) {
      return hash_combine(tuple_hash<Tuple, index - 1>::apply(t),
                          std::get<index>(t));
    }
  };
  template <class Tuple> struct tuple_hash<Tuple, size_t(-1)> {
    static uint64_t apply(const Tuple &t) { return 0; }
  };

 public:
  uint64_t operator()(const std::tuple<T...> &t) const {
    return tuple_hash<std::tuple<T...>>::apply(t);
  }
};
template <class hash_table> struct hash_table_wrapper : hash_table {
  using key_type = typename hash_table::key_type;
  size_t count(const key_type &key) const {
    return hash_table::find(key) != hash_table::end();
  }
  template <class... Args> auto emplace(Args &&... args) {
    return hash_table::insert(typename hash_table::value_type(args...));
  }
};
template <class Key, class Mapped = __gnu_pbds::null_type>
using cc_hash_table =
    hash_table_wrapper<__gnu_pbds::cc_hash_table<Key, Mapped, hash<Key>>>;
template <class Key, class Mapped = __gnu_pbds::null_type>
using gp_hash_table =
    hash_table_wrapper<__gnu_pbds::gp_hash_table<Key, Mapped, hash<Key>>>;
template <class Key, class Mapped>
using unordered_map = std::unordered_map<Key, Mapped, hash<Key>>;
template <class Key> using unordered_set = std::unordered_set<Key, hash<Key>>;
}  // namespace workspace
#line 3 "Library\\utils\\iostream_overload.hpp"
namespace std {
template <class T, class U> istream &operator>>(istream &is, pair<T, U> &p) {
  return is >> p.first >> p.second;
}
template <class T, class U>
ostream &operator<<(ostream &os, const pair<T, U> &p) {
  return os << p.first << ' ' << p.second;
}
template <class tuple_t, size_t index> struct tuple_is {
  static istream &apply(istream &is, tuple_t &t) {
    tuple_is<tuple_t, index - 1>::apply(is, t);
    return is >> get<index>(t);
  }
};
template <class tuple_t> struct tuple_is<tuple_t, SIZE_MAX> {
  static istream &apply(istream &is, tuple_t &t) { return is; }
};
template <class... T> istream &operator>>(istream &is, tuple<T...> &t) {
  return tuple_is<tuple<T...>, tuple_size<tuple<T...>>::value - 1>::apply(is,
                                                                          t);
}
template <class tuple_t, size_t index> struct tuple_os {
  static ostream &apply(ostream &os, const tuple_t &t) {
    tuple_os<tuple_t, index - 1>::apply(os, t);
    return os << ' ' << get<index>(t);
  }
};
template <class tuple_t> struct tuple_os<tuple_t, 0> {
  static ostream &apply(ostream &os, const tuple_t &t) {
    return os << get<0>(t);
  }
};
template <class tuple_t> struct tuple_os<tuple_t, SIZE_MAX> {
  static ostream &apply(ostream &os, const tuple_t &t) { return os; }
};
template <class... T> ostream &operator<<(ostream &os, const tuple<T...> &t) {
  return tuple_os<tuple<T...>, tuple_size<tuple<T...>>::value - 1>::apply(os,
                                                                          t);
}
template <class Container, typename Value = typename Container::value_type,
          enable_if_t<!is_same<decay_t<Container>, string>::value, nullptr_t> =
              nullptr>
istream &operator>>(istream &is, Container &cont) {
  for (auto &&e : cont) is >> e;
  return is;
}
template <class Container, typename Value = typename Container::value_type,
          enable_if_t<!is_same<decay_t<Container>, string>::value, nullptr_t> =
              nullptr>
ostream &operator<<(ostream &os, const Container &cont) {
  bool flag = 1;
  for (auto &&e : cont) flag ? flag = 0 : (os << ' ', 0), os << e;
  return os;
}
}  // namespace std
#line 3 "Library\\utils\\read.hpp"
namespace workspace {
// read with std::cin.
template <class T = void> struct read {
  typename std::remove_const<T>::type value;
  template <class... types> read(types... args) : value(args...) {
    std::cin >> value;
  }
  operator T() const { return value; }
};
template <> struct read<void> {
  template <class T> operator T() const {
    T value;
    std::cin >> value;
    return value;
  }
};
}  // namespace workspace
#line 13 "yu.cpp"

namespace workspace {
constexpr char eol = '\n';
using namespace std;
using i64 = int_least64_t;
using p32 = pair<int, int>;
using p64 = pair<i64, i64>;
template <class T, class Comp = std::less<T>>
using priority_queue = std::priority_queue<T, std::vector<T>, Comp>;
template <class T> using stack = std::stack<T, std::vector<T>>;
struct solver;
}  // namespace workspace
int main() { config::main<workspace::solver>(); }
unsigned config::cases() {
  // return -1; // not specify
  // int t; std::cin >> t; return t; // given
  return 1;
}

#line 4 "Library\\data_structure\\union_find\\basic.hpp"
struct union_find {
  union_find(const size_t &n = 0) : link(n, -1) {}

  size_t find(const size_t &x) {
    assert(x < size());
    return link[x] < 0 ? x : (link[x] = find(link[x]));
  }

  size_t size() const { return link.size(); }

  size_t size(const size_t &x) {
    assert(x < size());
    return -link[find(x)];
  }

  bool same(const size_t &x, const size_t &y) {
    assert(x < size() && y < size());
    return find(x) == find(y);
  }

  virtual bool unite(size_t x, size_t y) {
    assert(x < size() && y < size());
    x = find(x), y = find(y);
    if (x == y) return false;
    if (link[x] > link[y]) std::swap(x, y);
    link[x] += link[y];
    link[y] = x;
    return true;
  }

 protected:
  std::vector<int> link;
};  // class union_find
#line 5 "Library\\graph\\directed\\strongly_connected_components.hpp"
struct strongly_connected_components {
  strongly_connected_components(size_t n) : graph(n), low(n), made() {}

  // add an edge from the vertex s to the vertex t.
  void add_edge(size_t src, size_t dst) {
    assert(src < size());
    assert(dst < size());
    graph[src].emplace_back(dst);
    made = false;
  }

  // the number of the components.
  size_t count() {
    make();
    return comp_cnt;
  }

  size_t size() const { return graph.size(); }

  // the component which the vertex v belongs to.
  size_t operator[](size_t v) {
    make();
    return low[v];
  }

  // the directed acyclic graph consisting of the components.
  const std::vector<std::vector<size_t>> &shrinked_dag() {
    make();
    return dag;
  }

 protected:
  std::vector<std::vector<size_t>> graph, dag;
  std::vector<size_t> low;
  size_t comp_cnt;
  bool made;

  void make() {
    if (made) return;
    made = true, comp_cnt = 0;
    low.assign(size(), 0);
    size_t *itr = new size_t[size()];
    bool *const used = new bool[size()];
    for (size_t v{}, c{}; v != size(); ++v) affix(v, c, itr, used + size());
    delete[] itr;
    delete[] used;
    for (auto &e : low) e += comp_cnt;
    reverse(begin(dag), end(dag));
    for (auto &arcs : dag)
      for (auto &to : arcs) to += comp_cnt;
  }

  size_t affix(size_t src, size_t &c, size_t *&itr, bool *used) {
    if (low[src]) return low[src];
    size_t idx = ++c;
    low[src] = idx;
    *itr++ = src;
    for (size_t dst : graph[src])
      low[src] = std::min(low[src], affix(dst, c, itr, used));
    if (low[src] == idx) {
      ++comp_cnt;
      used[-comp_cnt] = true;
      dag.emplace_back(0);
      auto srcp = itr;
      do {
        low[*--srcp] = -comp_cnt;
      } while (*srcp != src);
      while (itr != srcp) {
        auto now = *--itr;
        for (auto to : graph[now]) {
          if (!used[(int)low[to]]) {
            dag.back().emplace_back(low[to]);
            used[(int)low[to]] = true;
          }
        }
      }
      for (int c : dag.back()) used[c] = false;
      used[-comp_cnt] = false;
      return idx;
    }
    return low[src];
  }
};  // class strongly_connected_components
#line 4 "Library\\modulus\\modint.hpp"
template <int_fast64_t mod = 0>  // compile-time defined modulo.
struct modint {
  static_assert(mod > 0);
  template <bool i32, class = void> struct modif {
    using value_type = int_least32_t;
  };
  template <class void_t> struct modif<false, void_t> {
    using value_type = int_least64_t;
  };
  using value_type = typename modif < mod<(1 << 30)>::value_type;
  constexpr static modint one() noexcept { return 1; }
  constexpr operator value_type() const noexcept { return value; }
  constexpr modint() noexcept = default;
  template <class int_type, std::enable_if_t<std::is_integral<int_type>::value,
                                             std::nullptr_t> = nullptr>
  constexpr modint(int_type n) noexcept : value((n %= mod) < 0 ? mod + n : n) {}
  constexpr modint operator++(int) noexcept {
    modint t{*this};
    return operator+=(1), t;
  }
  constexpr modint operator--(int) noexcept {
    modint t{*this};
    return operator-=(1), t;
  }
  constexpr modint &operator++() noexcept { return operator+=(1); }
  constexpr modint &operator--() noexcept { return operator-=(1); }
  constexpr modint operator-() const noexcept {
    return value ? mod - value : 0;
  }
  constexpr modint &operator+=(const modint &rhs) noexcept {
    return (value += rhs.value) < mod ? 0 : value -= mod, *this;
  }
  constexpr modint &operator-=(const modint &rhs) noexcept {
    return (value += mod - rhs.value) < mod ? 0 : value -= mod, *this;
  }
  constexpr modint &operator*=(const modint &rhs) noexcept {
    return value = (int_fast64_t)value * rhs.value % mod, *this;
  }
  constexpr modint &operator/=(const modint &rhs) noexcept {
    return operator*=(rhs.inverse());
  }
  template <class int_type, std::enable_if_t<std::is_integral<int_type>::value,
                                             std::nullptr_t> = nullptr>
  constexpr modint operator+(const int_type &rhs) const noexcept {
    return modint{*this} += rhs;
  }
  constexpr modint operator+(const modint &rhs) const noexcept {
    return modint{*this} += rhs;
  }
  template <class int_type, std::enable_if_t<std::is_integral<int_type>::value,
                                             std::nullptr_t> = nullptr>
  constexpr modint operator-(const int_type &rhs) const noexcept {
    return modint{*this} -= rhs;
  }
  constexpr modint operator-(const modint &rhs) const noexcept {
    return modint{*this} -= rhs;
  }
  template <class int_type, std::enable_if_t<std::is_integral<int_type>::value,
                                             std::nullptr_t> = nullptr>
  constexpr modint operator*(const int_type &rhs) const noexcept {
    return modint{*this} *= rhs;
  }
  constexpr modint operator*(const modint &rhs) const noexcept {
    return modint{*this} *= rhs;
  }
  template <class int_type, std::enable_if_t<std::is_integral<int_type>::value,
                                             std::nullptr_t> = nullptr>
  constexpr modint operator/(const int_type &rhs) const noexcept {
    return modint{*this} /= rhs;
  }
  constexpr modint operator/(const modint &rhs) const noexcept {
    return modint{*this} /= rhs;
  }
  template <class int_type, std::enable_if_t<std::is_integral<int_type>::value,
                                             std::nullptr_t> = nullptr>
  constexpr friend modint operator+(const int_type &lhs,
                                    const modint &rhs) noexcept {
    return modint(lhs) + rhs;
  }
  template <class int_type, std::enable_if_t<std::is_integral<int_type>::value,
                                             std::nullptr_t> = nullptr>
  constexpr friend modint operator-(const int_type &lhs,
                                    const modint &rhs) noexcept {
    return modint(lhs) - rhs;
  }
  template <class int_type, std::enable_if_t<std::is_integral<int_type>::value,
                                             std::nullptr_t> = nullptr>
  constexpr friend modint operator*(const int_type &lhs,
                                    const modint &rhs) noexcept {
    return modint(lhs) * rhs;
  }
  template <class int_type, std::enable_if_t<std::is_integral<int_type>::value,
                                             std::nullptr_t> = nullptr>
  constexpr friend modint operator/(const int_type &lhs,
                                    const modint &rhs) noexcept {
    return modint(lhs) / rhs;
  }
  constexpr modint inverse() const noexcept {
    assert(value);
    value_type a{mod}, b{value}, u{}, v{1}, t{};
    while (b)
      t = a / b, a ^= b ^= (a -= t * b) ^= b, u ^= v ^= (u -= t * v) ^= v;
    return {u};
  }
  constexpr static modint pow(modint rhs, int_fast64_t e) noexcept {
    if (e < 0) e = e % (mod - 1) + mod - 1;
    modint res{1};
    while (e) {
      if (e & 1) res *= rhs;
      rhs *= rhs, e >>= 1;
    }
    return res;
  }
  friend std::ostream &operator<<(std::ostream &os,
                                  const modint &rhs) noexcept {
    return os << rhs.value;
  }
  friend std::istream &operator>>(std::istream &is, modint &rhs) noexcept {
    int_fast64_t value;
    rhs = (is >> value, value);
    return is;
  }

 protected:
  value_type value = 0;
};           // class modint
template <>  // runtime defined modulo as default(mod = 0).
struct modint<0> {
  using value_type = int_fast64_t;
  static value_type &mod() noexcept {
    static value_type mod{};
    return mod;
  }
  static modint one() noexcept { return 1; }
  operator value_type() const noexcept { return value; }
  modint() noexcept = default;
  template <class int_type, std::enable_if_t<std::is_integral<int_type>::value,
                                             std::nullptr_t> = nullptr>
  modint(int_type n) noexcept
      : value{(assert(mod()), n %= mod() < 0 ? n + mod() : n)} {}
  modint operator++(int) noexcept {
    modint t{*this};
    return operator+=(1), t;
  }
  modint operator--(int) noexcept {
    modint t{*this};
    return operator-=(1), t;
  }
  modint &operator++() noexcept { return operator+=(1); }
  modint &operator--() noexcept { return operator-=(1); }
  modint operator-() const noexcept { return value ? mod() - value : 0; }
  modint &operator+=(const modint &rhs) noexcept {
    return (value += rhs.value) < mod() ? 0 : value -= mod(), *this;
  }
  modint &operator-=(const modint &rhs) noexcept {
    return (value += mod() - rhs.value) < mod() ? 0 : value -= mod(), *this;
  }
  modint &operator*=(const modint &rhs) noexcept {
    return (value *= rhs.value) %= mod(), *this;
  }
  modint &operator/=(const modint &rhs) noexcept {
    return operator*=(rhs.inverse());
  }
  template <class int_type, std::enable_if_t<std::is_integral<int_type>::value,
                                             std::nullptr_t> = nullptr>
  modint operator+(const int_type &rhs) const noexcept {
    return modint{*this} += rhs;
  }
  modint operator+(const modint &rhs) const noexcept {
    return modint{*this} += rhs;
  }
  template <class int_type, std::enable_if_t<std::is_integral<int_type>::value,
                                             std::nullptr_t> = nullptr>
  modint operator-(const int_type &rhs) const noexcept {
    return modint{*this} -= rhs;
  }
  modint operator-(const modint &rhs) const noexcept {
    return modint{*this} -= rhs;
  }
  template <class int_type, std::enable_if_t<std::is_integral<int_type>::value,
                                             std::nullptr_t> = nullptr>
  modint operator*(const int_type &rhs) const noexcept {
    return modint{*this} *= rhs;
  }
  modint operator*(const modint &rhs) const noexcept {
    return modint{*this} *= rhs;
  }
  template <class int_type, std::enable_if_t<std::is_integral<int_type>::value,
                                             std::nullptr_t> = nullptr>
  modint operator/(const int_type &rhs) const noexcept {
    return modint{*this} /= rhs;
  }
  modint operator/(const modint &rhs) const noexcept {
    return modint{*this} /= rhs;
  }
  template <class int_type, std::enable_if_t<std::is_integral<int_type>::value,
                                             std::nullptr_t> = nullptr>
  friend modint operator+(const int_type &lhs, const modint &rhs) noexcept {
    return modint(lhs) + rhs;
  }
  template <class int_type, std::enable_if_t<std::is_integral<int_type>::value,
                                             std::nullptr_t> = nullptr>
  friend modint operator-(const int_type &lhs, const modint &rhs) noexcept {
    return modint(lhs) - rhs;
  }
  template <class int_type, std::enable_if_t<std::is_integral<int_type>::value,
                                             std::nullptr_t> = nullptr>
  friend modint operator*(const int_type &lhs, const modint &rhs) noexcept {
    return modint(lhs) * rhs;
  }
  template <class int_type, std::enable_if_t<std::is_integral<int_type>::value,
                                             std::nullptr_t> = nullptr>
  friend modint operator/(const int_type &lhs, const modint &rhs) noexcept {
    return modint(lhs) / rhs;
  }
  modint inverse() const noexcept {
    assert(mod() && value);
    value_type a{mod()}, b{value}, u{}, v{1}, t{};
    while (b)
      t = a / b, a ^= b ^= (a -= t * b) ^= b, u ^= v ^= (u -= t * v) ^= v;
    return {u};
  }
  static modint pow(modint rhs, int_fast64_t e) noexcept {
    if (e < 0) e = e % (mod() - 1) + mod() - 1;
    modint res{1};
    while (e) {
      if (e & 1) res *= rhs;
      rhs *= rhs, e >>= 1;
    }
    return res;
  }
  friend std::ostream &operator<<(std::ostream &os,
                                  const modint &rhs) noexcept {
    return os << rhs.value;
  }
  friend std::istream &operator>>(std::istream &is, modint &rhs) noexcept {
    int_fast64_t value;
    rhs = modint((is >> value, value));
    return is;
  }

 protected:
  value_type value = 0;
};  // class modint<0>
using modint_runtime = modint<0>;
#line 35 "yu.cpp"

struct workspace::solver {
  using mint = modint<1000000007>;

  solver() {
    // start here!
    int n, m;
    cin >> n >> m;
    vector<p32> same, diff;
    vector<int> zero(n + 1, 0);
    for (int i = 0; i < m; i++) {
      int l, r, p;
      cin >> l >> r >> p;
      if (p) {
        if (p > 0)
          same.emplace_back(l - 1, r);
        else
          diff.emplace_back(l - 1, r);
      } else {
        zero[r - 1] = l;
      }
    }

    vector<int> nonz(1 + n);
    for (auto [l, r] : same) {
      nonz[l]++;
      nonz[r]--;
    }
    for (auto [l, r] : diff) {
      nonz[l]++;
      nonz[r]--;
    }
    partial_sum(begin(nonz), end(nonz), begin(nonz));

    mint ans{1};
    // 0-exclusive
    {
      int cnt = 0;
      for (int i = 0; i < n; i++) {
        if (nonz[i]) {
          cnt++;
        }
      }
      cnt -= size(same);
      cnt -= size(diff);
      ans = mint::pow(2, cnt);
    }
    // 0 can exist
    {
      mint acc;
      vector<mint> dp(n + 1);
      acc = dp[0] = 1;
      vector<mint> pow2{1};
      vector<int> cnt(n + 1);
      for (int i = 0, j = 0; i < n; i++) {
        cnt[i + 1] = cnt[i];
        if (!nonz[i]) {
          dp[i + 1] = acc;
          acc = acc * 2 + dp[i + 1];
          cnt[i + 1] += 1;
        }
        pow2.emplace_back(pow2.back() * 2);
        while (j < zero[i]) {
          acc -= dp[j] * pow2[cnt[i + 1] - cnt[j]];
          j++;
        }
      }
      ans *= acc;
    }
    cout << ans << eol;
  }
};