#include <cstdio>

 #include <queue>

 const int N = ;

 struct Edge {

     int v, nex, len;

 }edge[N << ]; int top;

 int in[N], topo[N], e[N], n, out[N];

 double p[N];

 inline void add(int x, int y, int z) {

     top++;

     edge[top].v = y;

     edge[top].len = z;

     edge[top].nex = e[x];

     e[x] = top;

     return;

 }

 inline void topo_sort() {

     std::queue<int> Q;

     for(int i = ; i <= n; i++) {

         if(!in[i]) {

             Q.push(i);

         }

     }

     int t = ;

     while(!Q.empty()) {

         int x = Q.front();

         Q.pop();

         topo[++t] = x;

         for(int i = e[x]; i; i = edge[i].nex) {

             int y = edge[i].v;

             in[y]--;

             if(!in[y]) {

                 Q.push(y);

             }

         }

     }

     return;

 }

 int main() {

     int m;

     scanf("%d%d", &n, &m);

     for(int i = , x, y, z; i <= m; i++) {

         scanf("%d%d%d", &x, &y, &z);

         add(x, y, z);

         in[y]++;

         out[x]++;

     }

     topo_sort();

     p[] = 1.0;

     double ans = 0.0;

     for(int a = ; a <= n; a++) {

         int x = topo[a];

         for(int i = e[x]; i; i = edge[i].nex) {

             int y = edge[i].v;

             p[y] += p[x] / out[x];

             ans += p[x] * edge[i].len / out[x];

         }

     }

     printf("%.2lf", ans);

     return ;

 }