#include <bits/stdc++.h>
#define eps 1e-8

using namespace std;

int n, m;
double rez[260];
double mat[260][260];

double gauss()
{
    for(int i = 0; i < n; i++)
    {
        if(abs(mat[i][i]) < eps)
        {
            for(int j = i + 1; j < n; j++)
                if(abs(mat[j][i]) >= eps)
                {
                    for(int k = i; k <= n; k++)
                        swap(mat[i][k], mat[j][k]);
                    break;
                }
        }
        double oneovermatii = 1. / mat[i][i];
        for(int j = i + 1; j <= n; j++)
            mat[i][j] *= oneovermatii;
        mat[i][i] = 1;
        for(int j = i + 1; j < n; j++)
        {
            if(abs(mat[j][i]) < eps) continue;
            for(int k = i + 1; k <= n; k++)
                mat[j][k] -= mat[j][i] * mat[i][k];
            mat[j][i] = 0;
        }
    }
    for(int i = n - 1; i >= 0; i--)
    {
        double sum = 0;
        for(int j = i + 1; j < n; j++)
            sum += rez[j] * mat[i][j];
        rez[i] = mat[i][n] - sum;
    }
    return rez[0];
}

int main()
{
    freopen("tunel.in", "r", stdin);
    freopen("tunel.out", "w", stdout);
    int a, b, c;
    scanf("%d%d", &n, &m);
    for(int i = 0; i < m; i++)
    {
        scanf("%d%d%d", &a, &b, &c);
        a--; b--;
        mat[a][a]--;
        mat[b][b]--;
        mat[a][b]++;
        mat[b][a]++;
        mat[a][n] -= c;
        mat[b][n] -= c;
    }
    for(int i = 0; i <= n; i++)
        mat[n - 1][i] = 0;
    mat[n - 1][n - 1] = 1;
    printf("%.3f", gauss());
    return 0;
}