#include <bits/stdc++.h>
#define MAXN 255
#define MAXM 255

const double EPS = 0.0000001;
inline double absolut(double a){return a > 0 ? a : -a;}
double a[1 + MAXN][1 + MAXM + 1], v[1 + MAXN];
std::vector <std::pair<int, int>> G[1 + MAXN];
int main(){
    FILE*fi,*fo;
    fi = fopen("tunel.in","r");
    fo = fopen("tunel.out","w");

    int n, m;
    fscanf(fi,"%d%d", &n, &m);
    for(int i = 1; i <= m; i++){
        int a, b, c;
        fscanf(fi,"%d%d%d", &a, &b, &c);
        G[a].push_back({b, c});
        G[b].push_back({a, c});
    }
    for(int i = 1; i < n; i++){
        a[i][i] = -1.0 * G[i].size();
        for(auto y: G[i]) a[i][y.first] += 1.0, a[i][n + 1] -= 1.0 * y.second;
    }
    for(int i = 1; i < n; i++) a[i][n] = 0.0;

    m = n, n--;
    int i, j, k;
    i = j = 1;
    while(i <= n && j <= m){
        k = i;
        while(k <= n && absolut(a[k][j]) < EPS) k++;
        if(k != n + 1){
            if(k != i) for(int p = 1; p <= m + 1; p++) std::swap(a[i][p], a[k][p]);
            for(int p = j + 1; p <= m + 1; p++) a[i][p] /= a[i][j];
            a[i][j] = 1.0;
            for(int p = i + 1; p <= n; p++){
                for(int q = j + 1; q <= m + 1; q++) a[p][q] -= a[p][j] * a[i][q];
                a[p][j] = 0.0;
            }
            i++;
        }
        j++;
    }

    for(int i = n; i >= 1; i--)
        for(int j = 1; j <= m + 1; j++)
            if(absolut(a[i][j]) > EPS){
                v[j] = a[i][m + 1];
                for(int k = j + 1; k <= m; k++) v[j] -= v[k] * a[i][k];
                break;
            }
    fprintf(fo,"%f", v[1]);

    return 0;
}