#include<bits/stdc++.h>

using namespace std;

#define re register int

#define ll long long

#define INF 0x3f3f3f3f

#define maxn 30009

#define maxm  10009

#define eps 1e-9

inline ll read()

{

    ll x=,f=;char ch=getchar();

    while(ch<''||ch>''){if(ch=='-')f=-;ch=getchar();}

    while(ch>=''&&ch<=''){x=(x<<)+(x<<)+(ll)(ch-'');ch=getchar();}

    return x*f;

}

bool flag;

bool vis[maxn];

double dis[maxn];

int head[maxn];

struct edge

{

    int to,nxt;

    double val;

}p[maxm];

int n,m,k,tot,cnt;

double ans,sum,l,r; 

void add(int x,int y,double z)

{

    ++cnt,p[cnt].to=y,p[cnt].nxt=head[x],p[cnt].val=z,head[x]=cnt;

}

void  Spfa(int u,double ave)

{

    if(flag)

        return ;

    vis[u]=;

    for(int i=head[u];i;i=p[i].nxt)

    {

        int v=p[i].to;

        if(dis[u]+p[i].val-ave<dis[v])

        {

            dis[v]=dis[u]+p[i].val-ave;

            if(!vis[v])

                Spfa(v,ave);

            if(flag)

                return ;

            else if(vis[v])

            {

                flag=true;

                return ;

            }

        }

    }

    vis[u]=;

}

bool Check(double ave)

{

    flag=false;

    memset(vis,,sizeof(vis));

    for(int j=;j<maxn;j++)

        dis[j]=;

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

    {

        Spfa(i,ave);

        if(flag)

            break;

    }

    return flag;

}

int main()

{

//    freopen(".in","r",stdin);

//    freopen(".out","w",stdout);

    n=read(),m=read();

    for(int i=;i<=m;i++)

    {

        int x=read(),y=read();

        double z;scanf("%lf",&z);

        add(x,y,z);

    }

    l=-1e7,r=1e7;

    while((r-l)>eps)

    {

        double mid=(l+r)/;

        if(Check(mid))

        {

            ans=mid;

            r=mid;

        }

        else

            l=mid;

    }

    printf("%0.8lf",ans);

    fclose(stdin);

    fclose(stdout);

    return ;

}