#include <fstream>
#include <iomanip>
#include <cmath>

using namespace std;

const double EPS = 1e-6;
int N, M;
double X[256];
double A[256][256 + 1];

ifstream f("tunel.in");
ofstream g("tunel.out");

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++)
        {
            if(abs(A[j][i]) <= EPS) continue;
            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()
{
    int a, b, c;
    f >> N >> M;
    while(M--)
    {
        f >> 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();
    g << fixed << setprecision(3) << X[1];
    return 0;
}