#include<bits/stdc++.h>
using namespace std;
const int N=1e3+5;
const int M=1e5+5;
int n,m;
struct node{
	int x,y,t;
}a[M];
bool cmp(node x,node y){
	return x.t<y.t;
}
int fa[N],siz[N];
int find(int x){
	return (x==fa[x]?x:fa[x]=find(fa[x]));
}
void merge(int x,int y){
	if(find(x)==find(y)) return;
	fa[find(x)]=find(y);
	siz[x]=siz[x]+siz[y];
	siz[y]=siz[x];
} 
int main(){
	cin>>n>>m;
	for(int i=1;i<=n;i++) fa[i]=i,siz[i]=1;
	for(int i=1;i<=m;i++)
		cin>>a[i].x>>a[i].y>>a[i].t;
	sort(a+1,a+m+1,cmp);
	for(int i=1;i<=m;i++){
		merge(a[i].x,a[i].y);
		if(siz[a[i].x]>=n){
			cout<<a[i].t;
			return 0;
		}
	}
	cout<<-1;
	return 0;
}

只AC了#1和#3