#include <fstream>
#include <algorithm>
#include <vector>
#include <iomanip>

#define pe pair<int,int>
#define mp make_pair
#define fi first
#define se second

using namespace std;

ifstream fin("tunel.in");
ofstream fout("tunel.out");

const int MAX_N=260;
const double EPS=0.0001;

vector<pe> A[MAX_N];

double a[MAX_N][MAX_N];
double d[MAX_N];

void scad(double a[MAX_N],double b[MAX_N],double c,int m) {
    for(int i=1;i<=m+1;i++) {
        a[i]+=b[i]*c;
    }
}

void gauss(int n,int m) {
    /*for(int i=1;i<=n;i++,fout<<endl) {
        for(int j=1;j<=m+1;j++) {
            fout<<a[i][j]<<' ';
        }
    }
    fout<<endl;
    */
    for(int j=1;j<=m;j++) {
        for(int i=1;i<=n;i++) {
            if(i==j) {
                continue;
            }
            if(a[i][j]<=EPS&&a[i][j]>=-EPS) {
                continue;
            }
            scad(a[i],a[j],-(a[i][j]/a[j][j]),m);
        }
    }
    
    for(int j=1;j<=m;j++) {
        d[j]=a[j][m+1]/a[j][j];
    }
}

int main() {
    int n,m;
    fin>>n>>m;
    fout<<setprecision(4)<<fixed;
    for(int i=1;i<=m;i++) {
        int a,b,c;
        fin>>a>>b>>c;
        A[a].push_back(mp(b,c));
        A[b].push_back(mp(a,c));
    }
    
    for(int i=1;i<n;i++) {
        double p=1.0/A[i].size();
        a[i][i]=1.0;
        for(auto it=A[i].begin();it!=A[i].end();it++) {
            a[i][n]+=p*it->se;
            if(it->fi!=n) {
                a[i][it->fi]-=p;
            }
        }
    }

    gauss(n-1,n-1);

    fout<<d[1];

    return 0;
}