#include <iostream>

#include <cstdio>

#include <algorithm>

#include <cstring>

#include <queue>

using namespace std;

typedef long long ll;

const int N=,M=1e4+;

const double eps=1e-;

inline int read(){

    char c=getchar();int x=,f=;

    while(c<''||c>''){if(c=='-')f=-;c=getchar();}

    while(c>=''&&c<=''){x=x*+c-'';c=getchar();}

    return x*f;

}

int n,m,u,v;

double w;

struct edge{

    int v,ne;

    double w;

}e[M];

int h[N],cnt=;

inline void ins(int u,int v,double w){

    cnt++;

    e[cnt].v=v;e[cnt].w=w;e[cnt].ne=h[u];h[u]=cnt;

}

double d[N],g;

int vis[N],cl;

bool dfs(int u){

    vis[u]=cl;

    for(int i=h[u];i;i=e[i].ne){

        int v=e[i].v;double w=e[i].w-g;

        if(d[v]>d[u]+w){

            d[v]=d[u]+w;

            if(vis[u]==vis[v]) return true;

            else if(dfs(v)) return true;

        }

    }

    vis[u]=;

    return false;

}

bool NegativeCircle(double mid){

    g=mid;

    memset(vis,,sizeof(vis));

    memset(d,,sizeof(d));

    for(cl=;cl<=n;cl++) if(dfs(cl)) return true;

    return false;

}

bool check(double mid){return NegativeCircle(mid);}

void solve(){

    double l=-1e7,r=1e7;

    while(r-l>eps){

        double mid=(l+r)/2.0;

        if(check(mid)) r=mid;

        else l=mid;

    }

    printf("%.8lf",l);

}

int main(){

    freopen("in","r",stdin);

    n=read();m=read();

    for(int i=;i<=m;i++){

        u=read(),v=read();

        scanf("%lf",&w);

        ins(u,v,w);

    }

    solve();

}