#include<cstdio>

 #include<iostream>

 #include<algorithm>

 using namespace std;

 int f[], ans;

 int num;

 struct node{

     int x, y, l;

 } a[];

 inline int cmp(node i, node j){

     return i.l < j.l;

 }

 inline int find(int x){

     if(f[x] != x)

         f[x] = find(f[x]);

     return f[x];

 }

 int main(){

     int n, m;

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

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

         f[i] = i;

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

         scanf("%d%d%d", &a[i].x, &a[i].y, &a[i].l);

     }

     sort(a+, a+m+, cmp);

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

         int r1 = find(a[i].x);

         int r2 = find(a[i].y);

         if(r1 != r2){

             f[r1] = r2;

             num++;//道路数量

             ans = max(ans, a[i].l);//时间

         }

     }

     if(num >= n - ) printf("%d", ans);

     else printf("-1");

     return ;

 }