#include<bits/stdc++.h>
#define maxN 105
#define maxM 5005
#define eps 1e-8
using namespace std;

long double gauss[maxN][maxN];
typedef struct tip
{
    int a,b,c;
};
bool seen[maxN];
tip edge[maxM];
vector<pair<int,int> > v[maxN];
inline void dfs(int nod)
{
    seen[nod]=1;
    for(vector<pair<int,int> >::iterator it=v[nod].begin();it!=v[nod].end();it++)
    {
        if(!seen[it->first]) dfs(it->first);
    }
}
int n,m,x,y,c;
long double sol[maxN],ans;
int main()
{
    freopen("flux.in","r",stdin);
    freopen("flux.out","w",stdout);
    scanf("%d%d",&n,&m);
    for(int i=1;i<=m;i++)
    {
        scanf("%d%d%d",&x,&y,&c);
        v[x].push_back({y,c});
        v[y].push_back({x,c});
        edge[i]={x,y,c};
    }
    dfs(1);
    if(!seen[n])
    {
        printf("%d\n",0.0);
        return 0;
    }
    gauss[1][1]=gauss[n][n]=1.0;
    gauss[n][n+1]=1.0;
    for(int i=2;i<n;i++)
    {
        gauss[i][i]=v[i].size();
        for(vector<pair<int,int> >::iterator it=v[i].begin();it!=v[i].end();it++)
        {
            gauss[i][it->first]=-1.0;
        }
    }

    int i=1,j=1;

    while(i<=n && j<=n)
    {
        int k;
        for(k=i;k<=n;k++)
        {
            if(gauss[k][j]<-eps || gauss[k][j]>eps) break;
        }
        if(k==(n+1))
        {
            j++;
            continue;
        }
        if(k!=i)
        {
            for(int u=1;u<=n+1;u++)
            {
                swap(gauss[i][u],gauss[k][u]);
            }
        }
        for(int u=j+1;u<=n+1;u++)
        {
            gauss[i][u]/=gauss[i][j];
        }
        gauss[i][j]=1;
        for(int u=i+1;u<=n;u++)
        {
            for(int l=j+1;l<=n+1;l++)
            {
                gauss[u][l]-=gauss[u][j]*gauss[i][l];
            }
            gauss[u][j]=0;
        }
        i++;
        j++;
    }
    for(int i=n;i>0;i--)
    {
        for(int j=1;j<=n+1;j++)
        {
            if(gauss[i][j]<-eps || gauss[i][j]>eps)
            {
                sol[j]=gauss[i][n+1];
                for(int k=j+1;k<=n;k++)
                {
                    sol[j]-=sol[k]*gauss[i][k];
                }
                break;
            }
        }
    }
    long double coef=1e10;
    for(int i=1;i<=m;i++)
    {
        coef=min(coef,edge[i].c/abs(sol[edge[i].b]-sol[edge[i].a]));
    }
    for(vector<pair<int,int> >::iterator it=v[1].begin();it!=v[1].end();it++)
    {
        ans=ans+sol[it->first]*coef;
    }
    printf("%.6lf\n",ans);
    return 0;
}