#include <algorithm>
#include <fstream>
#include <iomanip>
#include <vector>
using namespace std;
const int MAX_N = 260;

vector< pair<int, double> > graph[MAX_N];
double coef[MAX_N][MAX_N];
double times[MAX_N];

int main() {
    ifstream fin("tunel.in");
    ofstream fout("tunel.out");
    int n, m;
    fin >> n >> m;
    for(int i = 1; i <= m; ++ i) {
        int a, b; double c;
        fin >> a >> b >> c;
        graph[a].push_back(make_pair(b, c));
        graph[b].push_back(make_pair(a, c));
    }
    coef[1][1] = 1.0;
    for(int i = 2; i <= n; ++ i) {
        for(int j = 1; j <= n; ++ j) {
            coef[i][j] = 0.0;
        }
        coef[i][i] = -1.0;
        double degree = 1.0 / static_cast<double>(graph[i].size());
        for(vector< pair<int, double> > :: iterator it = graph[i].begin(); it != graph[i].end(); ++ it) {
            coef[i][it->first] += degree;
            coef[i][n + 1] -= degree * it->second;
        }
    }
    /**for(int i = 1; i <= n; ++ i) {
        for(int j = 1; j <= n; ++ j) {
            if(j > 1) {
                fout << "+ ";
            }
            fout << fixed << setw(3) << setprecision(1) << coef[i][j] << "*t(" << j << ") ";
        }
        fout << "= " << coef[i][n + 1] << "\n";
    }
    fout << "\n";**/
    for(int i = n; i > 1; -- i) {
        for(int j = 1; j < i; ++ j) {
            double multiplier = coef[j][i] / coef[i][i];
            for(int k = 1; k <= n + 1; ++ k) {
                coef[j][k] -= coef[i][k] * multiplier;
            }
        }
    }
    /**for(int i = 1; i <= n; ++ i) {
        for(int j = 1; j <= n; ++ j) {
            if(j > 1) {
                fout << "+ ";
            }
            fout << fixed << setw(3) << setprecision(1) << coef[i][j] << "*t(" << j << ") ";
        }
        fout << "= " << coef[i][n + 1] << "\n";
    }**/
    for(int i = 1; i <= n; ++ i) {
        for(int j = 1; j < i; ++ j) {
            coef[i][n + 1] -= coef[i][j] * times[j];
        }
        times[i] = coef[i][n + 1] / coef[i][i];
        //fout << " " << times[i];
    }
    fout << times[n];
    return 0;
}