func_code_string: #include <bits/stdc++.h>   using namespace std;   long long n, m, i, j, k, mod, dp[605][605], rd[605], xs[605][605], ans = 1;   vector<long long> ts, bi[605], nrd, ncd;   long long gcd(long long x, long long y) {     if (y == 0) return x;     return gcd(y, x % y);   }   long long lcm(long long x, long long y) { return x / gcd(x, y) * y; }   void dfs(int x) {     int i;     rd[x] = -1;     ts.push_back(x);     for (i = 0; i < bi[x].size(); i++) {       rd[bi[x][i]]--;       if (!rd[bi[x][i]]) {         dfs(bi[x][i]);       }     }   }   int main() {     ios_base::sync_with_stdio(0);     cin >> n >> m >> mod;     for (i = 1; i <= m; i++) {       int x, y;       cin >> x >> y;       bi[x].push_back(y);       rd[y]++;     }     for (i = 1; i <= n; i++) {       if (rd[i] == 0) nrd.push_back(i);       if (bi[i].size() == 0) ncd.push_back(i);     }     for (i = 0; i < nrd.size(); i++) {       dfs(nrd[i]);       dp[nrd[i]][nrd[i]] = 1;     }     for (i = 0; i < ts.size(); i++) {       for (j = 0; j < ts.size(); j++) {         for (k = 0; k < bi[ts[j]].size(); k++) {           dp[ts[i]][bi[ts[j]][k]] += dp[ts[i]][ts[j]];           dp[ts[i]][bi[ts[j]][k]] %= mod;         }       }     }     for (i = 0; i < nrd.size(); i++) {       for (j = 0; j < ncd.size(); j++) {         xs[i][j] = dp[nrd[i]][ncd[j]];       }     }     long long cnt = 0;     for (i = 0; i < ncd.size(); i++) {       for (j = i + 1; j < nrd.size(); j++) {         while (xs[j][i]) {           long long t = -xs[i][i] / xs[j][i];           for (k = i; k < nrd.size(); k++) {             xs[i][k] += t * xs[j][k];             xs[i][k] %= mod;             xs[i][k] += mod;             xs[i][k] %= mod;           }           for (k = i; k < nrd.size(); k++) {             swap(xs[i][k], xs[j][k]);           }           cnt++;         }       }     }     if (cnt & 1) ans = mod - 1;     for (i = 0; i < nrd.size(); i++) {       ans *= xs[i][i];       ans %= mod;     }     cout << ans;     return 0;   }   