#include <cstdio>

#include <cstring>

#include <algorithm>

#define eps 1e-9

#define N 3010

#define M 10010

using namespace std;

int n , m , head[N] , to[M] , next[M] , cnt , x[M] , y[M] , vis[N];

double len[M] , dis[N] , z[M];

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

{

    to[++cnt] = y , len[cnt] = z , next[cnt] = head[x] , head[x] = cnt;

}

bool dfs(int x)

{

    int i;

    vis[x] = 1;

    for(i = head[x] ; i ; i = next[i])

    {

        if(dis[to[i]] > dis[x] + len[i])

        {

            dis[to[i]] = dis[x] + len[i];

            if(vis[to[i]]) return 1;

            if(dfs(to[i])) return 1;

        }

    }

    vis[x] = 0;

    return 0;

}

bool judge(double mid)

{

    int i;

    memset(head , 0 , sizeof(head));

    memset(vis , 0 , sizeof(vis));

    memset(dis , 0 , sizeof(dis));

    cnt = 1;

    for(i = 1 ; i <= m ; i ++ ) add(x[i] , y[i] , z[i] - mid);

    for(i = 1 ; i <= n ; i ++ ) if(dfs(i)) return 1;

    return 0;

}

int main()

{

    int i;

    double l = 100000000.0 , r = -100000000.0 , mid;

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

    for(i = 1 ; i <= m ; i ++ ) scanf("%d%d%lf" , &x[i] , &y[i] , &z[i]) , l = min(l , z[i]) , r = max(r , z[i]);

    while(l <= r)

    {

        mid = (l + r) / 2;

        if(judge(mid)) r = mid - eps;

        else l = mid + eps;

    }

    printf("%.8lf\n" , (l + r) / 2);

    return 0;

}