結果

問題 No.1775 Love Triangle 2
ユーザー NyaanNyaanNyaanNyaan
提出日時 2021-12-21 22:37:58
言語 C++17
(gcc 12.3.0 + boost 1.83.0)
結果
AC  
実行時間 761 ms / 8,000 ms
コード長 16,894 bytes
コンパイル時間 7,332 ms
コンパイル使用メモリ 359,132 KB
実行使用メモリ 4,940 KB
最終ジャッジ日時 2023-10-13 19:54:41
合計ジャッジ時間 20,455 ms
ジャッジサーバーID
(参考情報)
judge13 / judge12
このコードへのチャレンジ
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テストケース

テストケース表示
入力 結果 実行時間
実行使用メモリ
testcase_00 AC 3 ms
4,928 KB
testcase_01 AC 2 ms
4,640 KB
testcase_02 AC 3 ms
4,852 KB
testcase_03 AC 3 ms
4,752 KB
testcase_04 AC 761 ms
4,640 KB
testcase_05 AC 756 ms
4,656 KB
testcase_06 AC 754 ms
4,660 KB
testcase_07 AC 297 ms
4,784 KB
testcase_08 AC 729 ms
4,640 KB
testcase_09 AC 11 ms
4,856 KB
testcase_10 AC 13 ms
4,640 KB
testcase_11 AC 11 ms
4,816 KB
testcase_12 AC 11 ms
4,656 KB
testcase_13 AC 12 ms
4,696 KB
testcase_14 AC 13 ms
4,924 KB
testcase_15 AC 18 ms
4,696 KB
testcase_16 AC 18 ms
4,636 KB
testcase_17 AC 24 ms
4,640 KB
testcase_18 AC 42 ms
4,644 KB
testcase_19 AC 12 ms
4,880 KB
testcase_20 AC 13 ms
4,696 KB
testcase_21 AC 11 ms
4,704 KB
testcase_22 AC 12 ms
4,720 KB
testcase_23 AC 11 ms
4,692 KB
testcase_24 AC 11 ms
4,700 KB
testcase_25 AC 13 ms
4,696 KB
testcase_26 AC 13 ms
4,700 KB
testcase_27 AC 12 ms
4,652 KB
testcase_28 AC 14 ms
4,700 KB
testcase_29 AC 49 ms
4,636 KB
testcase_30 AC 84 ms
4,692 KB
testcase_31 AC 127 ms
4,708 KB
testcase_32 AC 142 ms
4,652 KB
testcase_33 AC 131 ms
4,672 KB
testcase_34 AC 130 ms
4,700 KB
testcase_35 AC 109 ms
4,856 KB
testcase_36 AC 80 ms
4,760 KB
testcase_37 AC 53 ms
4,672 KB
testcase_38 AC 36 ms
4,816 KB
testcase_39 AC 65 ms
4,692 KB
testcase_40 AC 105 ms
4,940 KB
testcase_41 AC 121 ms
4,856 KB
testcase_42 AC 103 ms
4,680 KB
testcase_43 AC 80 ms
4,648 KB
testcase_44 AC 58 ms
4,856 KB
testcase_45 AC 102 ms
4,812 KB
testcase_46 AC 44 ms
4,692 KB
testcase_47 AC 13 ms
4,884 KB
testcase_48 AC 23 ms
4,696 KB
testcase_49 AC 47 ms
4,640 KB
testcase_50 AC 81 ms
4,700 KB
testcase_51 AC 124 ms
4,932 KB
testcase_52 AC 138 ms
4,656 KB
testcase_53 AC 128 ms
4,884 KB
testcase_54 AC 129 ms
4,704 KB
testcase_55 AC 107 ms
4,660 KB
testcase_56 AC 81 ms
4,936 KB
testcase_57 AC 57 ms
4,640 KB
testcase_58 AC 40 ms
4,640 KB
testcase_59 AC 71 ms
4,656 KB
testcase_60 AC 87 ms
4,720 KB
testcase_61 AC 97 ms
4,684 KB
testcase_62 AC 51 ms
4,760 KB
testcase_63 AC 48 ms
4,852 KB
testcase_64 AC 45 ms
4,700 KB
testcase_65 AC 18 ms
4,700 KB
testcase_66 AC 20 ms
4,640 KB
testcase_67 AC 19 ms
4,648 KB
testcase_68 AC 10 ms
4,820 KB
testcase_69 AC 16 ms
4,704 KB
testcase_70 AC 29 ms
4,636 KB
testcase_71 AC 33 ms
4,884 KB
testcase_72 AC 37 ms
4,760 KB
testcase_73 AC 34 ms
4,636 KB
testcase_74 AC 37 ms
4,692 KB
testcase_75 AC 37 ms
4,660 KB
testcase_76 AC 33 ms
4,648 KB
testcase_77 AC 37 ms
4,652 KB
testcase_78 AC 37 ms
4,816 KB
testcase_79 AC 16 ms
4,856 KB
testcase_80 AC 17 ms
4,644 KB
testcase_81 AC 24 ms
4,660 KB
testcase_82 AC 22 ms
4,660 KB
testcase_83 AC 28 ms
4,656 KB
testcase_84 AC 21 ms
4,708 KB
testcase_85 AC 27 ms
4,788 KB
testcase_86 AC 19 ms
4,924 KB
testcase_87 AC 25 ms
4,816 KB
testcase_88 AC 38 ms
4,716 KB
testcase_89 AC 25 ms
4,704 KB
権限があれば一括ダウンロードができます

ソースコード

diff #

/**
 *  date : 2021-12-21 22:37:50
 */

#define NDEBUG
using namespace std;

// intrinstic
#include <immintrin.h>

#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <cctype>
#include <cfenv>
#include <cfloat>
#include <chrono>
#include <cinttypes>
#include <climits>
#include <cmath>
#include <complex>
#include <cstdarg>
#include <cstddef>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <deque>
#include <fstream>
#include <functional>
#include <initializer_list>
#include <iomanip>
#include <ios>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <stack>
#include <streambuf>
#include <string>
#include <tuple>
#include <type_traits>
#include <typeinfo>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

// utility
namespace Nyaan {
using ll = long long;
using i64 = long long;
using u64 = unsigned long long;
using i128 = __int128_t;
using u128 = __uint128_t;

template <typename T>
using V = vector<T>;
template <typename T>
using VV = vector<vector<T>>;
using vi = vector<int>;
using vl = vector<long long>;
using vd = V<double>;
using vs = V<string>;
using vvi = vector<vector<int>>;
using vvl = vector<vector<long long>>;

template <typename T, typename U>
struct P : pair<T, U> {
  template <typename... Args>
  P(Args... args) : pair<T, U>(args...) {}

  using pair<T, U>::first;
  using pair<T, U>::second;

  T &x() { return first; }
  const T &x() const { return first; }
  U &y() { return second; }
  const U &y() const { return second; }

  P &operator+=(const P &r) {
    first += r.first;
    second += r.second;
    return *this;
  }
  P &operator-=(const P &r) {
    first -= r.first;
    second -= r.second;
    return *this;
  }
  P &operator*=(const P &r) {
    first *= r.first;
    second *= r.second;
    return *this;
  }
  P operator+(const P &r) const { return P(*this) += r; }
  P operator-(const P &r) const { return P(*this) -= r; }

  P operator*(const P &r) const { return P(*this) *= r; }

  P operator*(int r) const { return {first * r, second * r}; }

  P operator-() const { return P{-first, -second}; }
};

using pl = P<ll, ll>;
using pi = P<int, int>;
using vp = V<pl>;

constexpr int inf = 1001001001;
constexpr long long infLL = 4004004004004004004LL;

template <typename T>
int sz(const T &t) {
  return t.size();
}

template <typename T, typename U>
inline bool amin(T &x, U y) {
  return (y < x) ? (x = y, true) : false;
}
template <typename T, typename U>
inline bool amax(T &x, U y) {
  return (x < y) ? (x = y, true) : false;
}

template <typename T>
inline T Max(const vector<T> &v) {
  return *max_element(begin(v), end(v));
}
template <typename T>
inline T Min(const vector<T> &v) {
  return *min_element(begin(v), end(v));
}
template <typename T>
inline long long Sum(const vector<T> &v) {
  return accumulate(begin(v), end(v), 0LL);
}

template <typename T>
int lb(const vector<T> &v, const T &a) {
  return lower_bound(begin(v), end(v), a) - begin(v);
}
template <typename T>
int ub(const vector<T> &v, const T &a) {
  return upper_bound(begin(v), end(v), a) - begin(v);
}

constexpr long long TEN(int n) {
  long long ret = 1, x = 10;
  for (; n; x *= x, n >>= 1) ret *= (n & 1 ? x : 1);
  return ret;
}

template <typename T, typename U>
pair<T, U> mkp(const T &t, const U &u) {
  return make_pair(t, u);
}

template <typename T>
vector<T> mkrui(const vector<T> &v, bool rev = false) {
  vector<T> ret(v.size() + 1);
  if (rev) {
    for (int i = int(v.size()) - 1; i >= 0; i--) ret[i] = v[i] + ret[i + 1];
  } else {
    for (int i = 0; i < int(v.size()); i++) ret[i + 1] = ret[i] + v[i];
  }
  return ret;
};

template <typename T>
vector<T> mkuni(const vector<T> &v) {
  vector<T> ret(v);
  sort(ret.begin(), ret.end());
  ret.erase(unique(ret.begin(), ret.end()), ret.end());
  return ret;
}

template <typename F>
vector<int> mkord(int N, F f) {
  vector<int> ord(N);
  iota(begin(ord), end(ord), 0);
  sort(begin(ord), end(ord), f);
  return ord;
}

template <typename T>
vector<int> mkinv(vector<T> &v) {
  int max_val = *max_element(begin(v), end(v));
  vector<int> inv(max_val + 1, -1);
  for (int i = 0; i < (int)v.size(); i++) inv[v[i]] = i;
  return inv;
}

}  // namespace Nyaan

// bit operation
namespace Nyaan {
__attribute__((target("popcnt"))) inline int popcnt(const u64 &a) {
  return _mm_popcnt_u64(a);
}
inline int lsb(const u64 &a) { return a ? __builtin_ctzll(a) : 64; }
inline int ctz(const u64 &a) { return a ? __builtin_ctzll(a) : 64; }
inline int msb(const u64 &a) { return a ? 63 - __builtin_clzll(a) : -1; }
template <typename T>
inline int gbit(const T &a, int i) {
  return (a >> i) & 1;
}
template <typename T>
inline void sbit(T &a, int i, bool b) {
  if (gbit(a, i) != b) a ^= T(1) << i;
}
constexpr long long PW(int n) { return 1LL << n; }
constexpr long long MSK(int n) { return (1LL << n) - 1; }
}  // namespace Nyaan

// inout
namespace Nyaan {

template <typename T, typename U>
ostream &operator<<(ostream &os, const pair<T, U> &p) {
  os << p.first << " " << p.second;
  return os;
}
template <typename T, typename U>
istream &operator>>(istream &is, pair<T, U> &p) {
  is >> p.first >> p.second;
  return is;
}

template <typename T>
ostream &operator<<(ostream &os, const vector<T> &v) {
  int s = (int)v.size();
  for (int i = 0; i < s; i++) os << (i ? " " : "") << v[i];
  return os;
}
template <typename T>
istream &operator>>(istream &is, vector<T> &v) {
  for (auto &x : v) is >> x;
  return is;
}

void in() {}
template <typename T, class... U>
void in(T &t, U &... u) {
  cin >> t;
  in(u...);
}

void out() { cout << "\n"; }
template <typename T, class... U, char sep = ' '>
void out(const T &t, const U &... u) {
  cout << t;
  if (sizeof...(u)) cout << sep;
  out(u...);
}

void outr() {}
template <typename T, class... U, char sep = ' '>
void outr(const T &t, const U &... u) {
  cout << t;
  outr(u...);
}

struct IoSetupNya {
  IoSetupNya() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(15);
    cerr << fixed << setprecision(7);
  }
} iosetupnya;

}  // namespace Nyaan

// debug
namespace DebugImpl {

template <typename U, typename = void>
struct is_specialize : false_type {};
template <typename U>
struct is_specialize<
    U, typename conditional<false, typename U::iterator, void>::type>
    : true_type {};
template <typename U>
struct is_specialize<
    U, typename conditional<false, decltype(U::first), void>::type>
    : true_type {};
template <typename U>
struct is_specialize<U, enable_if_t<is_integral<U>::value, void>> : true_type {
};

void dump(const char& t) { cerr << t; }

void dump(const string& t) { cerr << t; }

void dump(const bool& t) { cerr << (t ? "true" : "false"); }

template <typename U,
          enable_if_t<!is_specialize<U>::value, nullptr_t> = nullptr>
void dump(const U& t) {
  cerr << t;
}

template <typename T>
void dump(const T& t, enable_if_t<is_integral<T>::value>* = nullptr) {
  string res;
  if (t == Nyaan::inf) res = "inf";
  if constexpr (is_signed<T>::value) {
    if (t == -Nyaan::inf) res = "-inf";
  }
  if constexpr (sizeof(T) == 8) {
    if (t == Nyaan::infLL) res = "inf";
    if constexpr (is_signed<T>::value) {
      if (t == -Nyaan::infLL) res = "-inf";
    }
  }
  if (res.empty()) res = to_string(t);
  cerr << res;
}

template <typename T, typename U>
void dump(const pair<T, U>&);
template <typename T>
void dump(const pair<T*, int>&);

template <typename T>
void dump(const T& t,
          enable_if_t<!is_void<typename T::iterator>::value>* = nullptr) {
  cerr << "[ ";
  for (auto it = t.begin(); it != t.end();) {
    dump(*it);
    cerr << (++it == t.end() ? "" : ", ");
  }
  cerr << " ]";
}

template <typename T, typename U>
void dump(const pair<T, U>& t) {
  cerr << "( ";
  dump(t.first);
  cerr << ", ";
  dump(t.second);
  cerr << " )";
}

template <typename T>
void dump(const pair<T*, int>& t) {
  cerr << "[ ";
  for (int i = 0; i < t.second; i++) {
    dump(t.first[i]);
    cerr << (i == t.second - 1 ? "" : ", ");
  }
  cerr << " ]";
}

void trace() { cerr << endl; }
template <typename Head, typename... Tail>
void trace(Head&& head, Tail&&... tail) {
  cerr << " ";
  dump(head);
  if (sizeof...(tail) != 0) cerr << ",";
  trace(forward<Tail>(tail)...);
}

}  // namespace DebugImpl

#ifdef NyaanDebug
#define trc(...)                            \
  do {                                      \
    cerr << "## " << #__VA_ARGS__ << " = "; \
    DebugImpl::trace(__VA_ARGS__);          \
  } while (0)
#else
#define trc(...) (void(0))
#endif

// macro
#define each(x, v) for (auto&& x : v)
#define each2(x, y, v) for (auto&& [x, y] : v)
#define all(v) (v).begin(), (v).end()
#define rep(i, N) for (long long i = 0; i < (long long)(N); i++)
#define repr(i, N) for (long long i = (long long)(N)-1; i >= 0; i--)
#define rep1(i, N) for (long long i = 1; i <= (long long)(N); i++)
#define repr1(i, N) for (long long i = (N); (long long)(i) > 0; i--)
#define reg(i, a, b) for (long long i = (a); i < (b); i++)
#define regr(i, a, b) for (long long i = (b)-1; i >= (a); i--)
#define fi first
#define se second
#define ini(...)   \
  int __VA_ARGS__; \
  in(__VA_ARGS__)
#define inl(...)         \
  long long __VA_ARGS__; \
  in(__VA_ARGS__)
#define ins(...)      \
  string __VA_ARGS__; \
  in(__VA_ARGS__)
#define in2(s, t)                           \
  for (int i = 0; i < (int)s.size(); i++) { \
    in(s[i], t[i]);                         \
  }
#define in3(s, t, u)                        \
  for (int i = 0; i < (int)s.size(); i++) { \
    in(s[i], t[i], u[i]);                   \
  }
#define in4(s, t, u, v)                     \
  for (int i = 0; i < (int)s.size(); i++) { \
    in(s[i], t[i], u[i], v[i]);             \
  }
#define die(...)             \
  do {                       \
    Nyaan::out(__VA_ARGS__); \
    return;                  \
  } while (0)

namespace Nyaan {
void solve();
}
int main() { Nyaan::solve(); }

//

namespace NimberImpl {
using u16 = uint16_t;
using u32 = uint32_t;
using u64 = uint64_t;

struct calc8 {
  u16 dp[1 << 8][1 << 8];
  constexpr calc8() : dp() {
    dp[0][0] = dp[0][1] = dp[1][0] = 0;
    dp[1][1] = 1;
    for (int e = 1; e <= 3; e++) {
      int p = 1 << e, q = p >> 1;
      u16 ep = 1u << p, eq = 1u << q;
      for (u16 i = 0; i < ep; i++) {
        for (u16 j = i; j < ep; j++) {
          if (i < eq && j < eq) continue;
          if (min(i, j) <= 1u) {
            dp[i][j] = dp[j][i] = i * j;
            continue;
          }
          u16 iu = i >> q, il = i & (eq - 1);
          u16 ju = j >> q, jl = j & (eq - 1);
          u16 u = dp[iu][ju], l = dp[il][jl];
          u16 ul = dp[iu ^ il][ju ^ jl];
          u16 uq = dp[u][eq >> 1];
          dp[i][j] = ((ul ^ l) << q) ^ uq ^ l;
          dp[j][i] = dp[i][j];
        }
      }
    }
  }
} constexpr c8;

struct calc16 {
 private:
  static constexpr u16 proot = 10279;
  static constexpr u32 ppoly = 92191;
  static constexpr int order = 65535;

  u16 base[16], exp[(1 << 18) + 100];
  int log[1 << 16];

  constexpr u16 d(u32 x) { return (x << 1) ^ (x < 32768u ? 0 : ppoly); }

  constexpr u16 naive(u16 i, u16 j) {
    if (min(i, j) <= 1u) return i * j;
    u16 q = 8, eq = 1u << 8;
    u16 iu = i >> q, il = i & (eq - 1);
    u16 ju = j >> q, jl = j & (eq - 1);
    u16 u = c8.dp[iu][ju];
    u16 l = c8.dp[il][jl];
    u16 ul = c8.dp[iu ^ il][ju ^ jl];
    u16 uq = c8.dp[u][eq >> 1];
    return ((ul ^ l) << q) ^ uq ^ l;
  }

 public:
  constexpr calc16() : base(), exp(), log() {
    base[0] = 1;
    for (int i = 1; i < 16; i++) base[i] = naive(base[i - 1], proot);
    exp[0] = 1;
    for (int i = 1; i < order; i++) exp[i] = d(exp[i - 1]);
    u16* pre = exp + order + 1;
    pre[0] = 0;
    for (int b = 0; b < 16; b++) {
      int is = 1 << b, ie = is << 1;
      for (int i = is; i < ie; i++) pre[i] = pre[i - is] ^ base[b];
    }
    for (int i = 0; i < order; i++) exp[i] = pre[exp[i]], log[exp[i]] = i;

    int ie = 2 * order + 30;
    for (int i = order; i < ie; i++) exp[i] = exp[i - order];
    for (unsigned int i = ie; i < sizeof(exp) / sizeof(u16); i++) exp[i] = 0;
    log[0] = ie + 1;
  }

  constexpr u16 prod(u16 i, u16 j) const { return exp[log[i] + log[j]]; }

  // exp[3] = 2^{15} = 32768
  constexpr u16 Hprod(u16 i, u16 j) const { return exp[log[i] + log[j] + 3]; }
  constexpr u16 H(u16 i) const { return exp[log[i] + 3]; }
  constexpr u16 H2(u16 i) const { return exp[log[i] + 6]; }
} constexpr c16;

constexpr u32 product32(u32 i, u32 j) {
  u16 iu = i >> 16, il = i & 65535;
  u16 ju = j >> 16, jl = j & 65535;
  u16 l = c16.prod(il, jl);
  u16 ul = c16.prod(iu ^ il, ju ^ jl);
  u16 uq = c16.Hprod(iu, ju);
  return (u32(ul ^ l) << 16) ^ uq ^ l;
}

// (+ : xor, x : nim product, * : integer product)
// i x j
// = (iu x ju + il x ju + iu x ji) * 2^{16}
// + (iu x ju x 2^{15}) + il x jl
//
// assign ju = 2^{15}, jl = 0s
// -> i x j
// = ((iu + il) x 2^{15}) * 2^{16} + (iu x 2^{15} x 2^{15})
constexpr u32 H(u32 i) {
  u16 iu = i >> 16;
  u16 il = i & 65535;
  return (u32(c16.H(iu ^ il)) << 16) ^ c16.H2(iu);
}

constexpr u64 product64(u64 i, u64 j) {
  u32 iu = i >> 32, il = i & u32(-1);
  u32 ju = j >> 32, jl = j & u32(-1);
  u32 l = product32(il, jl);
  u32 ul = product32(iu ^ il, ju ^ jl);
  u32 uq = H(product32(iu, ju));
  return (u64(ul ^ l) << 32) ^ uq ^ l;
}
}  // namespace NimberImpl

template <typename uint, uint (*prod)(uint, uint)>
struct NimberBase {
  using N = NimberBase;
  uint x;
  NimberBase() : x(0) {}
  NimberBase(uint _x) : x(_x) {}
  static N id0() { return {}; }
  static N id1() { return {1}; }

  N& operator+=(const N& p) {
    x ^= p.x;
    return *this;
  }
  N& operator-=(const N& p) {
    x ^= p.x;
    return *this;
  }
  N& operator*=(const N& p) {
    x = prod(x, p.x);
    return *this;
  }
  N operator+(const N& p) const { return x ^ p.x; }
  N operator-(const N& p) const { return x ^ p.x; }
  N operator*(const N& p) const { return prod(x, p.x); }
  bool operator==(const N& p) const { return x == p.x; }
  bool operator!=(const N& p) const { return x != p.x; }
  friend ostream& operator<<(ostream& os, const N& p) { return os << p.x; }
};

using Nimber32 = NimberBase<uint32_t, NimberImpl::product32>;
using Nimber64 = NimberBase<uint64_t, NimberImpl::product64>;

/**
 * @brief Nim Product
 * @docs docs/math/nim-product.md
 */


namespace my_rand {

// [0, 2^64 - 1)
uint64_t rng() {
  static uint64_t x_ =
      uint64_t(chrono::duration_cast<chrono::nanoseconds>(
                   chrono::high_resolution_clock::now().time_since_epoch())
                   .count()) *
      10150724397891781847ULL;
  x_ ^= x_ << 7;
  return x_ ^= x_ >> 9;
}

// [l, r)
int64_t randint(int64_t l, int64_t r) {
  assert(l < r);
  return l + rng() % (r - l);
}

// choose n numbers from [l, r) without overlapping
vector<long long> randset(int64_t l, int64_t r, int64_t n) {
  assert(l <= r && n <= r - l);
  unordered_set<int64_t> s;
  for (int64_t i = n; i; --i) {
    int64_t m = randint(l, r + 1 - i);
    if (s.find(m) != s.end()) m = r - i;
    s.insert(m);
  }
  vector<long long> ret;
  for (auto& x : s) ret.push_back(x);
  return ret;
}

// [0.0, 1.0)
double rnd() {
  union raw_cast {
    double t;
    uint64_t u;
  };
  constexpr uint64_t p = uint64_t(1023 - 64) << 52;
  return rng() * ((raw_cast*)(&p))->t;
}

template <typename T>
void randshf(vector<T>& v) {
  int n = v.size();
  for (int loop = 0; loop < 2; loop++)
    for (int i = 0; i < n; i++) swap(v[i], v[randint(0, n)]);
}

}  // namespace my_rand

using my_rand::randint;
using my_rand::randset;
using my_rand::randshf;
using my_rand::rnd;
using my_rand::rng;


using namespace Nyaan;

Nimber32 dp[2][2][128][128];
Nimber32 nx[2][2][128][128];
Nimber32 w[128][128];

void Nyaan::solve() {
  i64 N, M, X, Y, Z, u, v;
  cin >> N >> M >> X >> Y >> Z;
  --X, --Y, --Z;
  rep(i, N) rep(j, i) {
    unsigned x = unsigned(rng()) % unsigned(-1) + 1;
    w[i][j] = w[j][i] = x;
  }
  rep(i, M) {
    cin >> u >> v;
    --u, --v;
    w[u][v] = w[v][u] = 0;
  }
  // y 訪問済み / z 訪問済み / 今のマス / 前のマス
  dp[0][0][X][X] = 1;
  rep1(L, N) {
    memset(nx, 0, sizeof(nx));
    rep(ky, 2) rep(kz, 2) rep(c, N) rep(d, N) {
      if (w[c][d] == 0) continue;
      if (ky == 1 and d == Y) continue;
      if (kz == 1 and d == Z) continue;
      int nky = ky | (d == Y), nkz = kz | (d == Z);
      rep(p, N) if (p != d) nx[nky][nkz][d][c] += dp[ky][kz][c][p];
    }
    rep(ky, 2) rep(kz, 2) rep(i, N) rep(j, N) {
      if (w[i][j] != 0) nx[ky][kz][i][j] *= w[i][j];
    }
    swap(dp, nx);
    rep(i, N) if (dp[1][1][X][i] != 0) die(L);
  }
  die(-1);
}
0