#include <bits/stdc++.h>
using namespace std;
const int nmax = 270;
double c[nmax][nmax], a[nmax];

int main()
{
    freopen("tunel.in", "r", stdin);
    freopen("tunel.out", "w", stdout);
    int n, m, i, j, k, x, y, cost;
    scanf("%d %d", &n, &m);
    for(i=1; i<=m; i++)
    {
        scanf("%d %d %d", &x, &y, &cost);
        c[x][y]+=1;
        c[y][x]+=1;
        a[x]+=1;
        a[y]+=1;
        c[x][0] += (double)cost;
        c[y][0] += (double)cost;
    }
    for(i=1; i<n; i++)
        for(j=0; j<n; j++)
            c[i][j]=c[i][j]/a[i];

    for(i=2; i<n; i++)
        for(j=1; j<n; j++)
            for(k=0; k<n; k++)
                if(j!=i && k!=i)
                    c[j][k]+=c[i][k]* 1/(1-c[i][i])*c[j][i];

    printf("%lf\n", (1.0/(1.0-c[1][1]))*c[1][0]);
    fclose(stdin);
    fclose(stdout);
    return 0;
}