#include<bits/stdc++.h>
#define maxN 265
#define eps 1e-6
using namespace std;
int n,m,x,y,z;
double sol[maxN],a[maxN][maxN];
vector<pair<int,int> > v[maxN];
void RunGauss()
{
    int i=1;
    int j=1;
    while(i<=n && j<=n)
    {
        int u;
        for(u=i;u<=n;u++)
            if(abs(a[u][j])>eps) break;
        if(u==n+1) //Necunoscuta libera
        {
            j++;
            continue;
        }
        if(u!=i)
        {
            for(int k=j;k<=n+1;k++)
            {
                swap(a[i][k],a[u][k]);
            }
        }
        for(int u=j+1;u<=n+1;u++)
            a[i][u]/=a[i][j];
        a[i][j]=1;
        for(int u=i+1;u<=n;u++)
        {
            for(int k=j+1;k<=n+1;k++)
                a[u][k]-=a[u][j]*a[i][k];
            a[u][j]=0;
        }
        i++;
        j++;
    }
    for(int i=n;i>0;i--)
    {
        for(int j=1;j<=n+1;j++)
        {
            if(abs(a[i][j])>eps)
            {
                sol[j]=a[i][n+1];
                for(int k=j+1;k<=n;k++)
                    sol[j]-=sol[k]*a[i][k];
                break;
            }
        }
    }
}
int main()
{
    freopen("tunel.in","r",stdin);
    freopen("tunel.out","w",stdout);
    scanf("%d%d",&n,&m);
    for(int i=1;i<=m;i++)
    {
        scanf("%d%d%d",&x,&y,&z);
        v[x].push_back({y,z});
        v[y].push_back({x,z});
    }
    for(int i=1;i<=n;i++)
    {
        a[i][i]=-1.0;
        int sz=v[i].size();
        for(vector<pair<int,int> >::iterator it=v[i].begin();it!=v[i].end();it++)
        {
            a[i][(*it).first]+=1.0/sz;
            a[i][n+1]-=(double)(1.0*(*it).second/sz);
        }
    }
    RunGauss();
    printf("%.4lf\n",sol[1]);
    return 0;
}