#include <cstdio>

int N, M;
double X[256];
double A[256][256 + 1];

void gauss()
{
    for(int i = 1; i < N; i++)
    {
        for(int j = i + 1; j <= N + 1; j++)
            A[i][j] /= A[i][i];
        A[i][i] = 1;
        for(int j = i + 1; j < N; j++)
        {
            for(int k = i + 1; k <= N + 1; k++)
                A[j][k] -= A[j][i] * A[i][k];
            A[j][i] = 0;
        }
    }
}

void solutie()
{
    for(int i = N - 1; i >= 1; i--)
    {
        X[i] = A[i][N + 1];
        for(int j = i + 1; j < N; j++)
            X[i] -= X[j] * A[i][j];
    }
}

int main()
{
    freopen("tunel.in", "r", stdin);
    freopen("tunel.out", "w", stdout);
    scanf("%d%d", &N, &M);
    while(M--)
    {
        int a, b, c;
        scanf("%d%d%d", &a, &b, &c);
        A[a][a]++;
        A[b][b]++;
        A[a][b]--;
        A[b][a]--;
        A[a][N + 1] += c;
        A[b][N + 1] += c;
    }
    gauss();
    solutie();
    printf("%.3f", X[1]);
    return 0;
}