#include <cstdio>
#include <algorithm>
#include <cmath>
#include <vector>

#define EPS 0.00000001

FILE *fin = fopen("flux.in", "r");
FILE *fout = fopen("flux.out", "w");

#define MAXN 100

int c[MAXN + 1][MAXN + 1];
double a[MAXN + 1][MAXN + 1], v[MAXN + 1];
std::vector <int> g;

inline void gauss(int n) {
    int c = 2, sef = n;
    for (int i = 2; i < n; i++) {
        int l = i;
        while (l <= n && std::fabs(a[l][c]) < EPS)
            l++;
        if (l == n + 1) sef = c;
        else {
            if (l != i)
                for (int j = c; j <= n; j++)
                    std::swap(a[l][j], a[i][j]);
            for (int j = c + 1; j <= n; j++)
                a[i][j] /= a[i][c];
            a[i][c] = 1;
            for (l = i + 1; l <= n; l++) {
                for (int j = c + 1; j <= n; j++)
                    a[l][j] -= a[l][c] * a[i][j];
                a[l][c] = 0;
            }
        }
        c++;
    }
    v[sef] = 1;
    for (int i = n; i > 1; i--)
        for (int j = 2; j <= n; j++)
            v[i] -= v[j] * a[i][j];
}

int main() {
    int n, m;
    fscanf(fin, "%d%d", &n, &m);

    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= n; j++)
            c[i][j] = -1;

    for (int i = 0; i < m; i++) {
        int x, y, z;
        fscanf(fin, "%d%d%d", &x, &y, &z);

        if (c[x][y] == -1 || c[x][y] > z)
            c[x][y] = z, c[y][x] = z;

        a[x][y]++;
        a[x][x]--;

        a[y][x]++;
        a[y][y]--;

        if (x == 1)
            g.push_back(y);
        else if (y == 1)
            g.push_back(x);
    }

    gauss(n);

    double t = -1;
    for (int i = 1; i <= n; i++)
        for (int j = 1; j <= n; j++)
            if (c[i][j] != -1 && std::fabs(v[i] - v[j]) > EPS)
                if (t < -EPS || c[i][j] < std::fabs(v[i] - v[j]) * t)
                    t = c[i][j] / std::fabs(v[i] - v[j]);
    double ans = 0;
    if (t > -10)
        for (auto &x : g)
            ans += t * v[x];

    fprintf(fout, "%.3f\n", ans);

    fclose(fin);
    fclose(fout);
    return 0;
}