#include<fstream>
#include<cstdio>
#include<cmath>
#include<algorithm>
using namespace std;
int n,m,grad[260];
double A[260][260],sol[260];
double EPS=0.0000001;

void Citire()
{
	int i,j,x,y,c;
	ifstream fin("tunel.in");
	fin>>n>>m;
	for(i=1;i<=m;i++)
	{
		fin>>x>>y>>c;
		grad[x]++;
		grad[y]++;
		A[x][y]++;
		A[y][x]++;
		A[x][n+1]-=c;
		A[y][n+1]-=c;
	}
	for(i=1;i<=n;i++)
	{
		for(j=1;j<=n+1;j++)
			A[i][j]/=(double)grad[i];
		A[i][i]=-1.0;
	}
	for(i=1;i<=n+1;i++)
		A[n][i]=0.0;
	fin.close();
}

void Eliminarea_Gaussiana()
{
	int i,j,k,p;
	i=j=1;
	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(p=1;p<=n+1;p++)
				swap(A[i][p],A[k][p]);
		}
		for(k=j+1;k<=n+1;k++)
			A[i][k]/=A[i][j];
		A[i][j]=1.0;
		for(k=i+1;k<=n;k++)
		{
			for(p=j+1;p<=n+1;p++)
				A[k][p]-=A[k][j]*A[i][p];
			A[k][j]=0.0;
		}
		i++;
		j++;
	}
}

void Determinare_Necunoscute()
{
	freopen("tunel.out","w",stdout);
	int i,j,k;
	bool gasit;
	for(i=n-1;i>0;i--)
	{
		gasit=false;
		for(j=1;j<=n+1 && !gasit;j++)
		{
			if(A[i][j]>EPS || A[i][j]<-EPS)
			{
				gasit=true;
				sol[j]=A[i][n+1];
				for(k=j+1;k<=n;k++)
					sol[j]-=sol[k]*A[i][k];
			}
		}
	}
	printf("%.8lf\n",sol[1]);
}

int main()
{
	Citire();
	Eliminarea_Gaussiana();
	Determinare_Necunoscute();
	return 0;
}