#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define ull unsigned long long
#define ld long double
#define pii pair<int,int>
#define fi first
#define se second
#define pb push_back
#define clr(f,n) memset(f,0,sizeof(int)*(n))
#define cpy(f,g,n) memcpy(f,g,sizeof(int)*(n))
const int N=3000+5;
const int M=10000+5;
const double eps=1e-10;
struct sdf{
    int to,next;double w;
}eg[2*M];
int head[N],ne=0;
void add(int x,int y,double w){
    eg[++ne]={y,head[x],w};
    head[x]=ne;return ;
}
int n,m;
bool ins[N];
double dis[N];
bool spfa(int pt,double mid){
    ins[pt]=1;
    for (int i=head[pt];i!=0;i=eg[i].next){
        int v=eg[i].to;double w=eg[i].w-mid;
        if (dis[v]>dis[pt]+w){
            dis[v]=dis[pt]+w;
            if (ins[v]||spfa(v,mid)) return 1;
        }
    }
    ins[pt]=0;return 0;
}
bool chck(double mid){
    for (int i=1;i<=n;i++)ins[i]=dis[i]=0;
    for (int i=1;i<=n;i++)if (spfa(i,mid))return 1;
    return 0;
}
int main(){
	freopen ("minicycle.in","r",stdin);
	freopen ("minicycle.out","w",stdout);
	scanf("%d%d",&n,&m);
	for (int i=1;i<=m;i++){
	    int x,y;double w;
	    scanf("%d%d%lf",&x,&y,&w);
	    add(x,y,w);
    }
    double l=-1e7,r=1e7;
    while(fabs(l-r)>eps){
        double mid=(l+r)/2;
        
        if (chck(mid))r=mid;
        else l=mid;
    }
    printf("%.8lf\n",l);
}