#include <stdio.h>
#include <fstream>
#include <cmath>
#include <iomanip>
using namespace std;
ifstream f("flux.in");
ofstream g("flux.out");
const double eps=1E-8;
const double INF=1E+9;
const int DIM=101;
double C[DIM][DIM],m[DIM][DIM+1],F[DIM][DIM],X[DIM];
bool Viz[DIM],D[DIM][DIM];
int N,M;
double sol;
void gauss()
{
    int i=2,j=2,k,l;
    while(i<=N && j<=N)
    {

        for( k=i; k<=N; k++)
            if(abs(m[i][j])>=eps)
            {
                break;
            }
        if(k==N+1)
        {
            j++;
            continue;
        }
        if(k!=i)
            for(l=j; l<=N+1; i++)
            swap(m[i][l], m[k][l]);
        for(k=j+1; k<=N+1; k++)
            m[i][k]/=m[i][j];
        m[i][j]=1;
        for (k=i+1; k<=N; k++)
        {
            for(l=j+1; l<=N+1; l++)
                m[k][l]-=m[i][l]*m[k][j];
            m[k][j]=0;
        }
        i++;
        j++;
    }
}
void solutie()
{
    for(int i=N; i>=2; i--)
        for(int  j=i; j<=N; j++)
            if(abs(m[i][j]>eps))
            {
                X[j]=m[i][N+1];
                for(int t=j+1; t<=N; t++)
                    X[j]-=m[i][t]*X[t];
                break;
            }
}
void DFS(int nod)
{
    Viz[nod]=1;
    for(int i=1; i<=N; i++)
        if(D[nod][i])
        {
            F[nod][i]=X[i]-X[nod];
            if(!Viz[i])
                DFS(i);
        }
}
int main()
{
    int x,y,z;
    f>>N>>M;
    for(int i=1; i<=N; i++)
        for(int j=1; j<=N; j++)
            C[i][j]=INF;
    for(int i=1; i<=M; i++)
    {
        f>>x>>y>>z;
        if(z<C[x][y]) C[x][y]=C[y][x]=z;
        D[x][y]=D[y][x]=1;
        m[x][x]++;
        m[y][y]++;
        m[x][y]--;
        m[y][x]--;
    }
    m[N][N+1]=1;
    gauss();
    solutie();
    DFS(1);
    if(Viz[N])
    {
        sol=INF;
        for(int i=1; i<=N; i++)
            for(int j=1; j<=N; j++)
                if(D[i][j] && F[i][j]>0)
                    sol=min(sol,C[i][j]/F[i][j]);
    }
    g<<setprecision(3)<<fixed<<sol;
    return 0;
}