#include<cstdio>
#include<queue>
#include<vector>
#define inf 1000000
#define NMax 1005
using namespace std;

int nrq[NMax],inq[NMax],N;
double d[NMax];
vector<pair<int,int> > vc[NMax];
queue<int> Q;

int BellmanFord (double minus)
{
    int i,nxt,crt;
    double dst;
    for (i=1; i<=N; i++)
        d[i]=inf, nrq[i]=0, inq[i]=0;
    Q.push(0);
    d[0]=0;
    inq[0]=1;
    nrq[0]++;
    while (!Q.empty())
    {
        crt=Q.front();
        Q.pop(), inq[crt]=0;
        for (i=0; i<vc[crt].size(); i++)
        {
            nxt=vc[crt][i].first, dst=vc[crt][i].second;
            if (crt) dst-=minus;
            if (d[nxt]>=d[crt]+dst)
            {
                d[nxt]=d[crt]+dst;
                if (!inq[nxt])
                    if (nrq[nxt]>N)
                        return 1;
                    else
                    {
                        Q.push(nxt);
                        nrq[nxt]++;
                        inq[nxt]=1;
                    }
            }
        }
    }
    return 0;
}

int main ()
{
    int i,M,x,y,dd;
    double st,dr,mid,sol;
    freopen("ciclu.in","r",stdin);
    freopen("ciclu.out","w",stdout);
    scanf("%d%d",&N,&M);
    for (i=1; i<=M; i++)
    {
        scanf("%d%d%d",&x,&y,&dd);
        vc[x].push_back(make_pair(y,dd));
    }
    for (i=1; i<=N; i++)
        vc[0].push_back(make_pair(i,0));
    st=1, dr=1000;
    while (st<dr)
    {
        mid=(st+dr)/2;
        if (BellmanFord(mid))
            sol=mid, dr=mid-0.1;
        else
            st=mid+0,1;
    }
    printf("%.2lf\n",sol);
}