#include <bits/stdc++.h>
using namespace std;

const int DIM = 105;
const double EPS = 1e-6;

struct edge {
    int x, y, c;
};

vector <edge> E;

int n, m;
double val[DIM];
double a[DIM][DIM];

void gauss() {
    int c = 2;
    for (int i = 2; i <= n; i++) {
        int l = i;
        while (l <= n && fabs(a[l][c]) < EPS)
            l++;
        if (l <= n) {
            if (l != i)
                for (int j = c; j <= n; j++)
                    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++;
    }
    val[n] = 1;
    for (int i = n - 1; i > 1; i--)
        for (int j = 2; j <= n; j++)
            val[i] -= val[j] * a[i][j];
}

int main()
{
    freopen("flux.in", "r", stdin);
    freopen("flux.out", "w", stdout);

    scanf("%d%d", &n, &m);
    int x, y, c;
    for (int i = 1; i <= m ; ++i) {
        scanf("%d%d%d", &x, &y, &c);
        ++a[x][y]; --a[x][x];
        --a[y][y]; ++a[y][x];
        E.push_back({x, y, c});
    }
    a[n][n + 1] = 1.0;
    gauss();

    double Sol = 0;
    double inm = 0.0;

    bool ok = false;
    for (auto it : E) {
        if (it.x == 1 || it.y == 1) Sol = Sol + val[it.y] + val[it.x];

        if (val[it.x] == val[it.y]) continue ;

        if (it.c == 0) {
            printf("0");
            return 0;
        }

        ok = true;
        inm = max(inm, abs(val[it.y] - val[it.x]) / it.c);
    }

    if (!ok) printf("0");
    else printf("%0.3f", Sol / inm);

    return 0;
}