#include <stdio.h>
#include <string.h>
#include <vector>

using namespace std;

#define NMAX 300
#define eps 1e-8

double a[NMAX][NMAX];
int n, m;
double c[NMAX];
short uz[NMAX];
int grad[NMAX];
int x[100100], y[100100];
double cost[100100];

inline void swap(double &a, double &b)
{
	double aux = a;
	a = b;
	b= aux;
}

inline double ABS(double a) { return (a > 0) ? (a) : -(a); }

void read()
{
	scanf("%d %d", &n, &m);
	for(int i = 1; i <= m; ++i)
	{
        scanf("%d %d %lf", &x[i], &y[i], &cost[i]);
		++grad[x[i]], ++grad[y[i]];
    }
    for(int i = 1; i <= m; ++i)
    {
        a[x[i]][y[i]] += (double)1/grad[x[i]];
        c[x[i]] -= (double)cost[i]/grad[x[i]];
        a[y[i]][x[i]] += (double)1/grad[y[i]];
        c[y[i]] -= (double)cost[i]/grad[y[i]];
    }
    for(int i = 1; i <= n; ++i)
        a[i][i] = -1, a[i][n] = 0;
}

void print()
{
    printf("%d\n", n);
    int i, j;
    for(i = 1; i <= n; ++i, printf("\n"))
    {
        for(j = 1; j <= n; ++j)
            printf("%lf ", a[i][j]);
        printf("%lf ", c[i]);
    }
}

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

	read();
	
//  print();
//  return 0;
	int i, j, k;
	for(i = 1; i < n; ++i)
	{
		for(j = i; j < n; ++j)
			if(ABS(a[j][i]) > eps)
				break;
		for(k = 1; k < n; ++k)
			swap(a[i][k], a[j][k]); swap(c[i], c[j]);
		
		for(j = 1; j < n; ++j)
			if(j != i)
			{
                if(a[j][i] < eps) continue;

                double f = a[i][i]/a[j][i];
				for(k = 1; k < n; ++k)
					a[j][k] = a[j][k]*f - a[i][k];
				c[j] = c[j]*f - c[i];
			}
	}
	//print();

    //printf("%.3lf\n", s);
    if(a[1][1] > eps)
        printf("%.3lf\n", (double)c[1]/a[1][1]);
    else
       printf("%.3lf\n", (double)-c[1]/a[1][1]);
	return 0;
}