#include <fstream>
#include <iomanip>
#include <algorithm>
#define DIM 105
#define INF 1000000000
#define EPS 0.0000001
#define infile "flux.in"
#define outfile "flux.out"

using namespace std;

ifstream f(infile);
ofstream g(outfile);

int n, m, i, j, k, l, a, b;

double c, Res;

double C[DIM][DIM], A[DIM][DIM], X[DIM];

int D[DIM][DIM];

bool ok[DIM];

void DFS(int nod) {
	ok[nod] = 1;
	for (int i = 1; i <= n; ++i)
	if (ok[i] == 0 && D[nod][i] != 0)
		DFS(i);
}

int main() {
	f >> n >> m;
	for (i = 1; i <= n; ++i)
	for (j = 1; j <= n; ++j)
		C[i][j] = INF;
	for (i = 1; i <= m; ++i) {
		f >> a >> b >> c;
		C[a][b] = std::min(C[a][b], c);
		C[b][a] = C[a][b];
		++D[a][b]; ++D[b][a];
	}
	for (i = 2; i <= n; ++i)
	for (j = 1; j <= n; ++j) 
	if (i != j){
		A[i][j] = D[i][j];
		A[i][i] -= D[i][j];
	}
	A[n][n + 1] = -1;
	i = 2; j = 2;
	while (i <= n && j <= n) {
		for (k = i; k <= n; ++k)
		if (A[k][j] < -EPS || A[k][j] > EPS)
			break;
		if (k == n + 1) {
			++j;
			continue;
		}
		if (k != i)
		for (l = 1; l <= n + 1; ++l) {
			double tmp = A[i][l];
			A[i][l] = A[k][l];
			A[k][l] = tmp;
		}
		for (l = j + 1; l <= n + 1; ++l)
			A[i][l] /= A[i][j];
		A[i][j] = 1;
		for (k = i + 1; k <= n; ++k) {
			for (l = j + 1; l <= n + 1; ++l)
				A[k][l] -= A[i][l] * A[k][j];
			A[k][j] = 0;
		}
		++i; ++j;
	}
	for (i = n; i >= 2; --i)
	for (j = 2; j <= n + 1; ++j)
	if (A[i][j] < -EPS || 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;
	}
	DFS(1);
	if (!ok[n]) {
		g << "0.000";
		return 0;
	}
	Res = INF;
	for (i = 1; i <= n; ++i)
	for (j = 1; j <= n; ++j) {
		if (i == j || D[i][j] == 0)
			continue;
		double tmp = X[i] - X[j];
		if (tmp >= -EPS && tmp <= EPS)
			continue;
		if (tmp < 0)
			tmp = -tmp;
		Res = std::min(Res, C[i][j] / tmp);
	}
	g << setprecision(3) << fixed << Res;
	return 0;
}

//This room. This bullet. There's a bullet for everyone. And a time. And a place. Yes... maybe this is how it has to be. - 47