#include<bits/stdc++.h>

using namespace std;

const int N=;

int n,m,ecnt,hd[N],v[N],nxt[N],vis[N],used[N],tim[N];

double w[N],d[N];

bool spfa(int S,double k)

{

    queue<int>q;q.push(S);

    for(int i=;i<=n;i++)vis[i]=,tim[i]=,d[i]=1e18;

    d[S]=,tim[S]=;

    while(!q.empty())

    {

        int u=q.front();q.pop();vis[u]=,used[u]=;

        for(int i=hd[u];i;i=nxt[i])

        if(d[v[i]]>d[u]+w[i]-k)

        {

            d[v[i]]=d[u]+w[i]-k;

            if(!vis[v[i]])q.push(v[i]),vis[v[i]]=,tim[v[i]]++;

            if(tim[v[i]]>)return ;

        }

    }

    return ;

}

bool check(double val)

{

    memset(used,,sizeof used);

    for(int i=;i<=n;i++)if(!used[i]&&spfa(i,val))return ;

    return ;

}

int main()

{

    scanf("%d%d",&n,&m);

    for(int i=,x,y;i<=m;i++)

    {

        double z;scanf("%d%d%lf",&x,&y,&z);

        v[++ecnt]=y,nxt[ecnt]=hd[x],w[ecnt]=z,hd[x]=ecnt;

    }

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

    while(r-l>1e-)

    {

        double mid=(l+r)/;

        if(check(mid))r=mid;else l=mid;

    }

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

}