#include<bits/stdc++.h>
#define int long long
using namespace std;
const int N=1e5+5;
struct node{
	int x,y,t;
}a[N];
int n,m,fa[N];
int cmp(node a,node b){
	return a.t<b.t;
}
int find(int x){
	if (x==fa[x]) return x;
	else return find(fa[x]);
}
bool bl(){
	for (int i=2;i<=n;i++){
		if (find(fa[i])!=find(fa[i-1])) return 0;
	}
	return 1;
}
signed main(){
	cin>>n>>m;
	for (int i=1;i<=m;i++) cin>>a[i].x>>a[i].y>>a[i].t;
	sort(a+1,a+1+m,cmp);
	for (int i=1;i<=n;i++) fa[i]=i;
	for (int i=1;i<=m;i++){
		if (find(a[i].x)!=find(a[i].y)) fa[find(a[i].x)]=find(a[i].y);
		if (bl()){
			cout<<a[i].t;
			return 0;
		}
	}
	cout<<"-1";
	return 0;
}