#include <bits/stdc++.h>

using namespace std;

ifstream f("flux.in");
ofstream g("flux.out");

struct flux
{
    int x,y,c;
}v[5010];

int n,k,col,m,i,j;
double mini=INT_MAX,suma,a[105][105],sol[105];

int main()
{
    f>>n>>m;
    for(i=1; i<=m; i++)
    {
        f>>v[i].x>>v[i].y>>v[i].c;

        a[v[i].x][v[i].x]++;
        a[v[i].y][v[i].y]++;

        a[v[i].x][v[i].y]--;
        a[v[i].y][v[i].x]--;
    }

    for(i=1; i<=n+1; i++)
    {
        a[1][i]=0;
    }
    a[1][1]=1;
    a[n][n+1]=1;

    // facem gauss
    i=1;
    j=1;
    while(i<=n && j<=n)
    {
        k=i;
        while(a[k][j]==0 && k<=n)k++;

        if(k==n+1)
        {
            j++;
            continue;
        }

        if(i!=k)
        {
            for(col=j; col<=n; col++)swap(a[i][col],a[k][col]);
        }

        for(col=j+1; col<=n; col++)
            a[i][col]=a[i][col]/a[i][j];
        a[i][j]=1;

        for(k=i+1; k<=n; k++)
        {
            for(col=j+1; col<=n+1; col++)
                a[k][col]-=a[k][j]*a[i][col];
            a[k][j]=0;
        }

        i++;
        j++;
    }

    // aflam x-urile
    for(i=n; i>=1; i--)
    {
        for(j=1; j<=n+1; j++)
            if(abs(a[i][j])>0.0001)
            {
                if(j==m+1)
                {
                    g<<0<<'\n';
                    return 0;
                }

                sol[j]=a[i][n+1];
                for(k=j+1;k<=n;k++)
                    sol[j]-=sol[k]*a[i][k];

                break;
            }
    }

    for(i=1;i<=m;i++)
    {
        double rez=v[i].c/(abs(sol[v[i].x]-sol[v[i].y]));
        mini=min(mini,rez);
    }

    if(mini==INT_MAX)
    {
        g<<0;
        return 0;
    }

    for(i=1;i<=m;i++)
    {
        if(v[i].x==n || v[i].y==n)
        {
            suma=suma+mini*abs(sol[v[i].x]-sol[v[i].y]);
        }
    }

    g<<fixed<<setprecision(6)<<suma;
    return 0;
}