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

using namespace std;

ifstream fin("tunel.in");
ofstream fout("tunel.out");

const int NMax = 255;
const double EPS = 0.001;

int N, M, Grade[NMax + 5], SumC[NMax + 5];
double A[NMax + 5][NMax + 5], X[NMax + 5];

vector <int> G[NMax + 5];

int main()
{
    fin >> N >> M;

    for(int i = 1, x, y, c; i <= M; i++)
    {
        fin >> x >> y >> c;

        Grade[x]++, Grade[y]++;
        SumC[x] += c, SumC[y] += c;

        G[x].push_back(y);
        G[y].push_back(x);
    }

    for(int i = 1; i < N; i++)
    {
        A[i][i] = -Grade[i];

        for(auto Nei : G[i])
            A[i][Nei] += 1;

        A[i][N + 1] = -SumC[i];
    }
    ///X[N] = 0
    A[N][N] = 1;

    int i = 1, j = 1, k;
    double ct;

    while(i <= N && j <= N)
    {
        for(k = i; k <= N; k++)
            if(fabs(A[k][j]) > EPS)
                break;

        if(k == N + 1)
        {
            j++;
            continue;
        }

        swap(A[i], A[k]);
        ct = A[i][j];

        for(k = j; k <= N + 1; k++)
            A[i][k] /= ct;

        for(int x = i + 1; x <= N; x++)
        {
            ct = A[x][j];

            for(int y = j; y <= N + 1; y++)
                A[x][y] -= ct * A[i][y];
        }
        i++, j++;
    }

    for(i = N; i > 0; i--)
        for(j = 1; j <= N; j++)
            if(fabs(A[i][j]) > EPS)
            {
                X[j] = A[i][N + 1];

                for(k = j + 1; k <= N; k++)
                    X[j] -= X[k] * A[i][k];

                break;
            }

    fout << fixed << setprecision(5) << X[1] << '\n';

    fin.close();
    fout.close();

    return 0;
}