#include <cstdio>#include <cstring>#include <algorithm>#include <queue>#define inc(i,j,k) for(int i=j;i<=k;i++)#define maxn 3010#define INF 0x3fffffffusing namespace std;inline int read(){    char ch=getchar(); int f=1,x=0;    while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=-1; ch=getchar();}    while(ch>=‘0‘&&ch<=‘9‘)x=x*10+ch-‘0‘,ch=getchar();    return f*x;}struct e{int t; double w; int n;}es[maxn*4]; int g[maxn],ess;void pe(int f,int t){es[++ess]=(e){t,0,g[f]}; g[f]=ess;}double w[maxn*4]; int n,m;void rebuild(double x){inc(i,1,m)es[i].w=w[i]-x;}bool ins[maxn],f; double d[maxn];void dfs(int x){    ins[x]=1;    for(int i=g[x];i;i=es[i].n){        if(f)return;        if(d[es[i].t]>d[x]+es[i].w){            if(ins[es[i].t]){f=1; return;} d[es[i].t]=d[x]+es[i].w; dfs(es[i].t);        }    }    ins[x]=0;}bool spfa(){    memset(ins,0,sizeof(ins)); memset(d,0,sizeof(d)); f=0;    inc(i,1,n){dfs(i); if(f)return 0;} return 1;}int main(){    n=read(); m=read(); inc(i,1,m){int x=read(),y=read(); scanf("%lf",&w[i]); pe(x,y);}    double l=-10000000,r=10000000; int t=60;    while(t--){        double mid=(l+r)/2; rebuild(mid); if(!spfa())r=mid;else l=mid;    }    printf("%.8lf",l); return 0;}