#include<cstdio>#include<iostream>#include<cstring>#include<cstdlib>#include<algorithm>#include<cmath>#include<queue>#include<deque>#include<set>#include<map>#include<ctime>#define LL long long#define inf 0x7ffffff#define pa pair<int,int>#define pi 3.1415926535897932384626433832795028841971#define eps 1e-10using namespace std;inline LL read(){    LL x=0,f=1;char ch=getchar();    while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=-1;ch=getchar();}    while(ch>=‘0‘&&ch<=‘9‘){x=x*10+ch-‘0‘;ch=getchar();}    return x*f;}inline void write(LL a){    if (a<0){printf("-");a=-a;}    if (a>=10)write(a/10);    putchar(a%10+‘0‘);}inline void writeln(LL a){write(a);printf("\n");}struct edge{	int to,next;	double v,v0;}e[100010];int n,m,cnt;bool fnd,mrk[100010];int head[100010];double dist[100010];double l=-1000000000.0,r=1000000000.0,ans=0.0;inline void ins(int u,int v,double w){	e[++cnt].to=v;	e[cnt].v0=w;	e[cnt].next=head[u];	head[u]=cnt;}inline void spfa(int x){	mrk[x]=1;	for (int i=head[x];i;i=e[i].next)		if (dist[e[i].to]>dist[x]+e[i].v)		{			if (mrk[e[i].to]){fnd=1;return;}			dist[e[i].to]=dist[x]+e[i].v;			spfa(e[i].to);			if (fnd)return;		}	mrk[x]=0;}inline bool jud(){	fnd=0;	memset(mrk,0,sizeof(mrk));	memset(dist,0,sizeof(dist));	for (int i=1;i<=n;i++)	{		spfa(i);		if (fnd)return 0;	}	return 1;}int main(){	n=read();m=read();	for(int i=1;i<=m;i++)	{		int x=read(),y=read();		double z;scanf("%lf",&z);		ins(x,y,z);	}	while (r-l>=eps)	{		double mid=(l+r)/2;		for (int i=1;i<=n;i++)			for (int j=head[i];j;j=e[j].next)				e[j].v=(e[j].v0-mid);		if (jud()){ans=mid;l=mid;}		else r=mid;	}	printf("%.8lf\n",ans);}