#include<cstdio>

#include<algorithm>

#include<cstring>

#define eps 1e-10

using namespace std;

const int maxn =  + ;

const int maxm =  + ;

int g[maxn],v[maxm],next[maxm],eid;

double w[maxm],dist[maxn],e[maxm],c;

bool vis[maxn];

int n,m;

void addedge(int a,int b,double c) {

    v[eid]=b; w[eid]=c; next[eid]=g[a]; g[a]=eid++;

}

void build() {

    memset(g,-,sizeof(g));

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

    for(int i=,a,b;i<=m;i++) {

        scanf("%d%d%lf",&a,&b,&c);

        addedge(a,b,c);

    }

}

bool dfs(int u) {

    vis[u]=;

    for(int i=g[u];~i;i=next[i]) if(dist[v[i]]>dist[u]+e[i]) {

        if(vis[v[i]]) return true;

        dist[v[i]]=dist[u]+e[i];

        if(dfs(v[i])) return true;

    }

    vis[u]=;

    return false;

}

bool calc() {

    memset(dist,,sizeof(dist));

    memset(vis,,sizeof(vis));

    for(int i=;i<=n;i++) if(dfs(i)) return ;

    return ;

}

void solve() {

    double l = -1e9,r=1e9,mid;

    while(r-l>=eps) {

        mid=(l+r)/;

        for(int u=;u<=n;u++)

        for(int i=g[u];~i;i=next[i])

            e[i]=w[i]+mid;

        if(calc()) l=mid;

        else r=mid;

    }

    printf("%.8lf\n",-l);

}

int main() {

    build();

    solve();

    return ;

}