#include #ifndef ATCODER_INTERNAL_BITOP_HPP #define ATCODER_INTERNAL_BITOP_HPP 1 #ifdef _MSC_VER #include #endif namespace atcoder { namespace internal { // @param n `0 <= n` // @return minimum non-negative `x` s.t. `n <= 2**x` int ceil_pow2(int n) { int x = 0; while ((1U << x) < (unsigned int)(n)) x++; return x; } // @param n `1 <= n` // @return minimum non-negative `x` s.t. `(n & (1 << x)) != 0` int bsf(unsigned int n) { #ifdef _MSC_VER unsigned long index; _BitScanForward(&index, n); return index; #else return __builtin_ctz(n); #endif } } // namespace internal } // namespace atcoder #endif // ATCODER_INTERNAL_BITOP_HPP #ifndef ATCODER_INTERNAL_MATH_HPP #define ATCODER_INTERNAL_MATH_HPP 1 #include namespace atcoder { namespace internal { // @param m `1 <= m` // @return x mod m constexpr long long safe_mod(long long x, long long m) { x %= m; if (x < 0) x += m; return x; } // Fast moduler by barrett reduction // Reference: https://en.wikipedia.org/wiki/Barrett_reduction // NOTE: reconsider after Ice Lake struct barrett { unsigned int _m; unsigned long long im; // @param m `1 <= m` barrett(unsigned int m) : _m(m), im((unsigned long long)(-1) / m + 1) {} // @return m unsigned int umod() const { return _m; } // @param a `0 <= a < m` // @param b `0 <= b < m` // @return `a * b % m` unsigned int mul(unsigned int a, unsigned int b) const { // [1] m = 1 // a = b = im = 0, so okay // [2] m >= 2 // im = ceil(2^64 / m) // -> im * m = 2^64 + r (0 <= r < m) // let z = a*b = c*m + d (0 <= c, d < m) // a*b * im = (c*m + d) * im = c*(im*m) + d*im = c*2^64 + c*r + d*im // c*r + d*im < m * m + m * im < m * m + 2^64 + m <= 2^64 + m * (m + 1) < 2^64 * 2 // ((ab * im) >> 64) == c or c + 1 unsigned long long z = a; z *= b; #ifdef _MSC_VER unsigned long long x; _umul128(z, im, &x); #else unsigned long long x = (unsigned long long)(((unsigned __int128)(z)*im) >> 64); #endif unsigned int v = (unsigned int)(z - x * _m); if (_m <= v) v += _m; return v; } }; // @param n `0 <= n` // @param m `1 <= m` // @return `(x ** n) % m` constexpr long long pow_mod_constexpr(long long x, long long n, int m) { if (m == 1) return 0; unsigned int _m = (unsigned int)(m); unsigned long long r = 1; unsigned long long y = safe_mod(x, m); while (n) { if (n & 1) r = (r * y) % _m; y = (y * y) % _m; n >>= 1; } return r; } // Reference: // M. Forisek and J. Jancina, // Fast Primality Testing for Integers That Fit into a Machine Word // @param n `0 <= n` constexpr bool is_prime_constexpr(int n) { if (n <= 1) return false; if (n == 2 || n == 7 || n == 61) return true; if (n % 2 == 0) return false; long long d = n - 1; while (d % 2 == 0) d /= 2; for (long long a : {2, 7, 61}) { long long t = d; long long y = pow_mod_constexpr(a, t, n); while (t != n - 1 && y != 1 && y != n - 1) { y = y * y % n; t <<= 1; } if (y != n - 1 && t % 2 == 0) { return false; } } return true; } template constexpr bool is_prime = is_prime_constexpr(n); // @param b `1 <= b` // @return pair(g, x) s.t. g = gcd(a, b), xa = g (mod b), 0 <= x < b/g constexpr std::pair inv_gcd(long long a, long long b) { a = safe_mod(a, b); if (a == 0) return {b, 0}; // Contracts: // [1] s - m0 * a = 0 (mod b) // [2] t - m1 * a = 0 (mod b) // [3] s * |m1| + t * |m0| <= b long long s = b, t = a; long long m0 = 0, m1 = 1; while (t) { long long u = s / t; s -= t * u; m0 -= m1 * u; // |m1 * u| <= |m1| * s <= b // [3]: // (s - t * u) * |m1| + t * |m0 - m1 * u| // <= s * |m1| - t * u * |m1| + t * (|m0| + |m1| * u) // = s * |m1| + t * |m0| <= b auto tmp = s; s = t; t = tmp; tmp = m0; m0 = m1; m1 = tmp; } // by [3]: |m0| <= b/g // by g != b: |m0| < b/g if (m0 < 0) m0 += b / s; return {s, m0}; } // Compile time primitive root // @param m must be prime // @return primitive root (and minimum in now) constexpr int primitive_root_constexpr(int m) { if (m == 2) return 1; if (m == 167772161) return 3; if (m == 469762049) return 3; if (m == 754974721) return 11; if (m == 998244353) return 3; int divs[20] = {}; divs[0] = 2; int cnt = 1; int x = (m - 1) / 2; while (x % 2 == 0) x /= 2; for (int i = 3; (long long)(i)*i <= x; i += 2) { if (x % i == 0) { divs[cnt++] = i; while (x % i == 0) { x /= i; } } } if (x > 1) { divs[cnt++] = x; } for (int g = 2;; g++) { bool ok = true; for (int i = 0; i < cnt; i++) { if (pow_mod_constexpr(g, (m - 1) / divs[i], m) == 1) { ok = false; break; } } if (ok) return g; } } template constexpr int primitive_root = primitive_root_constexpr(m); } // namespace internal } // namespace atcoder #endif // ATCODER_INTERNAL_MATH_HPP #ifndef ATCODER_INTERNAL_QUEUE_HPP #define ATCODER_INTERNAL_QUEUE_HPP 1 #include namespace atcoder { namespace internal { template struct simple_queue { std::vector payload; int pos = 0; void reserve(int n) { payload.reserve(n); } int size() const { return int(payload.size()) - pos; } bool empty() const { return pos == int(payload.size()); } void push(const T &t) { payload.push_back(t); } T &front() { return payload[pos]; } void clear() { payload.clear(); pos = 0; } void pop() { pos++; } }; } // namespace internal } // namespace atcoder #endif // ATCODER_INTERNAL_QUEUE_HPP #ifndef ATCODER_INTERNAL_SCC_HPP #define ATCODER_INTERNAL_SCC_HPP 1 #include #include #include namespace atcoder { namespace internal { template struct csr { std::vector start; std::vector elist; csr(int n, const std::vector> &edges) : start(n + 1), elist(edges.size()) { for (auto e : edges) { start[e.first + 1]++; } for (int i = 1; i <= n; i++) { start[i] += start[i - 1]; } auto counter = start; for (auto e : edges) { elist[counter[e.first]++] = e.second; } } }; // Reference: // R. Tarjan, // Depth-First Search and Linear Graph Algorithms struct scc_graph { public: scc_graph(int n) : _n(n) {} int num_vertices() { return _n; } void add_edge(int from, int to) { edges.push_back({from, {to}}); } // @return pair of (# of scc, scc id) std::pair> scc_ids() { auto g = csr(_n, edges); int now_ord = 0, group_num = 0; std::vector visited, low(_n), ord(_n, -1), ids(_n); visited.reserve(_n); auto dfs = [&](auto self, int v) -> void { low[v] = ord[v] = now_ord++; visited.push_back(v); for (int i = g.start[v]; i < g.start[v + 1]; i++) { auto to = g.elist[i].to; if (ord[to] == -1) { self(self, to); low[v] = std::min(low[v], low[to]); } else { low[v] = std::min(low[v], ord[to]); } } if (low[v] == ord[v]) { while (true) { int u = visited.back(); visited.pop_back(); ord[u] = _n; ids[u] = group_num; if (u == v) break; } group_num++; } }; for (int i = 0; i < _n; i++) { if (ord[i] == -1) dfs(dfs, i); } for (auto &x : ids) { x = group_num - 1 - x; } return {group_num, ids}; } std::vector> scc() { auto ids = scc_ids(); int group_num = ids.first; std::vector counts(group_num); for (auto x : ids.second) counts[x]++; std::vector> groups(ids.first); for (int i = 0; i < group_num; i++) { groups[i].reserve(counts[i]); } for (int i = 0; i < _n; i++) { groups[ids.second[i]].push_back(i); } return groups; } private: int _n; struct edge { int to; }; std::vector> edges; }; } // namespace internal } // namespace atcoder #endif // ATCODER_INTERNAL_SCC_HPP #ifndef ATCODER_INTERNAL_TYPE_TRAITS_HPP #define ATCODER_INTERNAL_TYPE_TRAITS_HPP 1 #include #include #include namespace atcoder { namespace internal { #ifndef _MSC_VER template using is_signed_int128 = typename std::conditional::value || std::is_same::value, std::true_type, std::false_type>::type; template using is_unsigned_int128 = typename std::conditional::value || std::is_same::value, std::true_type, std::false_type>::type; template using make_unsigned_int128 = typename std::conditional::value, __uint128_t, unsigned __int128>; template using is_integral = typename std::conditional::value || is_signed_int128::value || is_unsigned_int128::value, std::true_type, std::false_type>::type; template using is_signed_int = typename std::conditional<(is_integral::value && std::is_signed::value) || is_signed_int128::value, std::true_type, std::false_type>::type; template using is_unsigned_int = typename std::conditional<(is_integral::value && std::is_unsigned::value) || is_unsigned_int128::value, std::true_type, std::false_type>::type; template using to_unsigned = typename std::conditional< is_signed_int128::value, make_unsigned_int128, typename std::conditional::value, std::make_unsigned, std::common_type>::type>::type; #else template using is_integral = typename std::is_integral; template using is_signed_int = typename std::conditional::value && std::is_signed::value, std::true_type, std::false_type>::type; template using is_unsigned_int = typename std::conditional::value && std::is_unsigned::value, std::true_type, std::false_type>::type; template using to_unsigned = typename std::conditional::value, std::make_unsigned, std::common_type>::type; #endif template using is_signed_int_t = std::enable_if_t::value>; template using is_unsigned_int_t = std::enable_if_t::value>; template using to_unsigned_t = typename to_unsigned::type; } // namespace internal } // namespace atcoder #endif // ATCODER_INTERNAL_TYPE_TRAITS_HPP #ifndef ATCODER_MODINT_HPP #define ATCODER_MODINT_HPP 1 #include #include #include #ifdef _MSC_VER #include #endif namespace atcoder { namespace internal { struct modint_base { }; struct static_modint_base : modint_base { }; template using is_modint = std::is_base_of; template using is_modint_t = std::enable_if_t::value>; } // namespace internal template * = nullptr> struct static_modint : internal::static_modint_base { using mint = static_modint; public: static constexpr int mod() { return m; } static mint raw(int v) { mint x; x._v = v; return x; } static_modint() : _v(0) {} template * = nullptr> static_modint(T v) { long long x = (long long)(v % (long long)(umod())); if (x < 0) x += umod(); _v = (unsigned int)(x); } template * = nullptr> static_modint(T v) { _v = (unsigned int)(v % umod()); } static_modint(bool v) { _v = ((unsigned int)(v) % umod()); } unsigned int val() const { return _v; } mint &operator++() { _v++; if (_v == umod()) _v = 0; return *this; } mint &operator--() { if (_v == 0) _v = umod(); _v--; return *this; } mint operator++(int) { mint result = *this; ++*this; return result; } mint operator--(int) { mint result = *this; --*this; return result; } mint &operator+=(const mint &rhs) { _v += rhs._v; if (_v >= umod()) _v -= umod(); return *this; } mint &operator-=(const mint &rhs) { _v -= rhs._v; if (_v >= umod()) _v += umod(); return *this; } mint &operator*=(const mint &rhs) { unsigned long long z = _v; z *= rhs._v; _v = (unsigned int)(z % umod()); return *this; } mint &operator/=(const mint &rhs) { return *this = *this * rhs.inv(); } mint operator+() const { return *this; } mint operator-() const { return mint() - *this; } mint pow(long long n) const { assert(0 <= n); mint x = *this, r = 1; while (n) { if (n & 1) r *= x; x *= x; n >>= 1; } return r; } mint inv() const { if (prime) { assert(_v); return pow(umod() - 2); } else { auto eg = internal::inv_gcd(_v, m); assert(eg.first == 1); return eg.second; } } friend mint operator+(const mint &lhs, const mint &rhs) { return mint(lhs) += rhs; } friend mint operator-(const mint &lhs, const mint &rhs) { return mint(lhs) -= rhs; } friend mint operator*(const mint &lhs, const mint &rhs) { return mint(lhs) *= rhs; } friend mint operator/(const mint &lhs, const mint &rhs) { return mint(lhs) /= rhs; } friend bool operator==(const mint &lhs, const mint &rhs) { return lhs._v == rhs._v; } friend bool operator!=(const mint &lhs, const mint &rhs) { return lhs._v != rhs._v; } private: unsigned int _v; static constexpr unsigned int umod() { return m; } static constexpr bool prime = internal::is_prime; }; template struct dynamic_modint : internal::modint_base { using mint = dynamic_modint; public: static int mod() { return (int)(bt.umod()); } static void set_mod(int m) { assert(1 <= m); bt = internal::barrett(m); } static mint raw(int v) { mint x; x._v = v; return x; } dynamic_modint() : _v(0) {} template * = nullptr> dynamic_modint(T v) { long long x = (long long)(v % (long long)(mod())); if (x < 0) x += mod(); _v = (unsigned int)(x); } template * = nullptr> dynamic_modint(T v) { _v = (unsigned int)(v % mod()); } dynamic_modint(bool v) { _v = ((unsigned int)(v) % mod()); } unsigned int val() const { return _v; } mint &operator++() { _v++; if (_v == umod()) _v = 0; return *this; } mint &operator--() { if (_v == 0) _v = umod(); _v--; return *this; } mint operator++(int) { mint result = *this; ++*this; return result; } mint operator--(int) { mint result = *this; --*this; return result; } mint &operator+=(const mint &rhs) { _v += rhs._v; if (_v >= umod()) _v -= umod(); return *this; } mint &operator-=(const mint &rhs) { _v += mod() - rhs._v; if (_v >= umod()) _v -= umod(); return *this; } mint &operator*=(const mint &rhs) { _v = bt.mul(_v, rhs._v); return *this; } mint &operator/=(const mint &rhs) { return *this = *this * rhs.inv(); } mint operator+() const { return *this; } mint operator-() const { return mint() - *this; } mint pow(long long n) const { assert(0 <= n); mint x = *this, r = 1; while (n) { if (n & 1) r *= x; x *= x; n >>= 1; } return r; } mint inv() const { auto eg = internal::inv_gcd(_v, mod()); assert(eg.first == 1); return eg.second; } friend mint operator+(const mint &lhs, const mint &rhs) { return mint(lhs) += rhs; } friend mint operator-(const mint &lhs, const mint &rhs) { return mint(lhs) -= rhs; } friend mint operator*(const mint &lhs, const mint &rhs) { return mint(lhs) *= rhs; } friend mint operator/(const mint &lhs, const mint &rhs) { return mint(lhs) /= rhs; } friend bool operator==(const mint &lhs, const mint &rhs) { return lhs._v == rhs._v; } friend bool operator!=(const mint &lhs, const mint &rhs) { return lhs._v != rhs._v; } private: unsigned int _v; static internal::barrett bt; static unsigned int umod() { return bt.umod(); } }; template internal::barrett dynamic_modint::bt = 998244353; using modint998244353 = static_modint<998244353>; using modint1000000007 = static_modint<1000000007>; using modint = dynamic_modint<-1>; namespace internal { template using is_static_modint = std::is_base_of; template using is_static_modint_t = std::enable_if_t::value>; template struct is_dynamic_modint : public std::false_type { }; template struct is_dynamic_modint> : public std::true_type { }; template using is_dynamic_modint_t = std::enable_if_t::value>; } // namespace internal } // namespace atcoder #endif // ATCODER_MODINT_HPP #pragma GCC optimize("Ofast") #pragma GCC optimize("O3") #pragma GCC optimize("unroll-loops") #pragma GCC target("avx") #include #define _GLIBCXX_DEBUG using namespace std; using namespace atcoder; using ll = long long; using vec = vector; using vect = vector; using Graph = vector>; #define endl '\n' #define loop(i, n) for (register int i = 0; i < n; i++) #define Loop(i, m, n) for (int i = m; i < n; i++) #define pool(i, n) for (int i = n; i >= 0; i--) #define Pool(i, m, n) for (int i = n; i >= m; i--) #define modd 1000000007ll //#define modd 998244353ll #define flagcount(bit) __builtin_popcount(bit) #define flag(x) (1ll << x) #define flagadd(bit, x) bit |= flag(x) #define flagpop(bit, x) bit &= ~flag(x) #define flagon(bit, i) bit &flag(i) #define flagoff(bit, i) !(bit & (1ll << i)) #define all(v) v.begin(), v.end() #define low2way(v, x) lower_bound(all(v), x) #define high2way(v, x) upper_bound(all(v), x) #define idx_lower(v, x) (distance(v.begin(), low2way(v, x))) //配列vでx未満の要素数を返す #define idx_upper(v, x) (distance(v.begin(), high2way(v, x))) //配列vでx以下の要素数を返す #define idx_lower2(v, x) (v.size() - idx_lower(v, x)) //配列vでx以上の要素数を返す #define idx_upper2(v, x) (v.size() - idx_upper(v, x)) //配列vでxより大きい要素の数を返す #define putout(a) cout << a << '\n' #define Sum(v) accumulate(all(v), 0ll) ll ctoi(char c) { if (c >= '0' && c <= '9') { return c - '0'; } return -1; } template string make_string(T N) { string ret; T now = N; while (now > 0) { T x = now % 10; ret += (char)('0' + x); now /= 10; } reverse(all(ret)); return ret; } template T gcd(T a, T b) { if (a % b == 0) { return (b); } else { return (gcd(b, a % b)); } } template T lcm(T x, T y) { T z = gcd(x, y); return x * y / z; } template bool primejudge(T n) { if (n < 2) return false; else if (n == 2) return true; else if (n % 2 == 0) return false; double sqrtn = sqrt(n); for (T i = 3; i < sqrtn + 1; i++) { if (n % i == 0) { return false; } i++; } return true; } template bool chmax(T &a, const T &b) { if (a < b) { a = b; // aをbで更新 return true; } return false; } template bool chmin(T &a, const T &b) { if (a > b) { a = b; // aをbで更新 return true; } return false; } //場合によって使い分ける //const ll dx[4]={1,0,-1,0}; //const ll dy[4]={0,1,0,-1}; const ll dx[8] = {1, 1, 0, -1, -1, -1, 0, 1}; const ll dy[8] = {0, 1, 1, 1, 0, -1, -1, -1}; //cout << fixed << setprecision(10); //vector> field(h, vector(w)); using mint = modint1000000007; mint modpow(mint a, long long n) { mint res = 1; while (n > 0) { if (n & 1) res = res * a; a *= a; n >>= 1; } return res; } mint modinv(mint a) { return modpow(a, modd - 2); } vector fact(3000001); //fact[i]=(i!) vector factinv(3000001); //factinv[i]=(i!)^-1 void COMinit() { mint now = 1; fact[0] = 1; factinv[0] = modinv(0); for (long long i = 1; i < 3000001; i++) { now *= i; fact[i] = now; factinv[i] = modinv(now); } } mint COM(long long n, long long r) { if (n < r) return 0; if (n < 0 || r < 0) return 0; if (n == r) return 1; if (r == 0) return 1; mint ans = fact[n]; ans *= factinv[r]; ans *= factinv[n - r]; return ans; } int main() { COMinit(); ll N, K; cin >> N >> K; N++; vector B(K + 1, -1); B[0] = 1; for (ll i = 1; i <= K; i++) { B[i] *= modinv(i + 1); mint S = 0; for (ll k = 0; k <= i - 1; k++) { mint x = COM(1 + i, k); x *= B[k]; S += x; } B[i] *= S; } vector pown(K + 2); pown[0] = 1; loop(i, K + 1) pown[i + 1] = pown[i] * N; mint ans = modinv(K + 1); mint SUM = 0; for (ll i = 0; i <= K; i++) { mint x = COM(K + 1, i); x *= B[i]; x *= pown[K + 1 - i]; SUM += x; } ans *= SUM; putout(ans.val()); return 0; }