func_code_string: #include <bits/stdc++.h>   using namespace std;   const int N = 510;   const long long INF = 1e18;   inline int read() {     int x = 0, f = 1;     char ch = getchar();     while (ch <  0  || ch >  9 ) {       if (ch ==  - ) f = -1;       ch = getchar();     }     while (ch >=  0  && ch <=  9 ) {       x = x * 10 + ch -  0 ;       ch = getchar();     }     return x * f;   }   int n, m, now;   bitset<N> f[2][70][N], g, tmp;   long long ans, fac[N];   int main() {     n = read();     m = read();     for (int i = 1, u, v, w; i <= m; i++) {       u = read();       v = read();       w = read();       f[w][0][u][v] = 1;     }     for (int i = 1; i <= 60; i++)       for (int u = 1; u <= n; u++)         for (int v = 1; v <= n; v++) {           if (f[0][i - 1][u][v] != 0) f[0][i][u] |= f[1][i - 1][v];           if (f[1][i - 1][u][v] != 0) f[1][i][u] |= f[0][i - 1][v];         }     if (f[0][60][1].count()) {       puts( -1 );       return 0;     }     fac[0] = 1;     for (int i = 1; i <= 60; i++) fac[i] = fac[i - 1] * 2;     now = 0;     tmp[1] = 1;     for (int i = 60; i >= 0; i--) {       g.reset();       for (int j = 1; j <= n; j++)         if (tmp[j]) g |= f[now][i][j];       if (g.count() != 0) {         now ^= 1;         tmp = g;         ans += fac[i];       }     }     if (ans > INF)       puts( -1 );     else       printf( %lld n , ans);     return 0;   }   