#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
const int N=100010,M=200010;

int n,m;
int h[N],e[M],w[M],ne[M],idx;
int dout[N];
double f[N];

void add(int a,int b,int c)
{
    e[idx]=b,w[idx]=c,ne[idx]=h[a],h[a]=idx++;

}

double dp(int u)
{
    if(f[u]>=0)return f[u];
    f[u]=0;
    for(int i=h[u];~i;i=ne[i])
    {
        int j=e[i];
        f[u]+=(w[i]+dp(j))/dout[u];
    }
    return f[u];
}



int main()
{
    scanf("%d%d", &n, &m);
    memset(h, -1, sizeof h);

    for (int i = 0; i < m; i ++ )
    {
        int a, b, c;
        scanf("%d%d%d", &a, &b, &c);
        add(a, b, c);
        dout[a] ++ ;
    }

    memset(f, -1, sizeof f);

    printf("%.2lf\n", dp(1));

    return 0;
}