#define  _CRT_SECURE_NO_WARNINGS
#include <iostream>
using namespace std;
#include <algorithm>
#include <string>
#include <vector>
#include <list>
#include <set>
#include <map>
#include <queue>
#include <stack>
#include <unordered_set>
#include <unordered_map>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>

map<int, pair<int, int>>T;//修复那条
int vallige[1003];//村庄
int N, M;
int find(int x) {
	if (vallige[x] == x)
		return x;
	return vallige[x] = find(vallige[x]);
}
bool IS(int t) {
	for (auto a : T) {
		if (a.first > t)
			break;
		else {
			if (find(a.second.first) != find(a.second.second))
				vallige[find(a.second.first)] = vallige[find(a.second.second)];
		}
	}
    //验证合理性
	int root = find(vallige[1]);
	for (int i = 1; i <= N; i++) {
		if (find(vallige[i]) != root)
			return false;
	}
	return true;
}

int main() {

	cin >> N >> M; 
	for (int i = 0; i < M; i++) {
		int a, b, c;
		cin >> a >> b >> c;

		T[c] = { a,b };
	}
    //二分查找满足要求的t
	int l = 0, r = 100005;
	while (l + 1 != r) {
		int mid = (l + r) / 2;
		for (int i = 1; i <= N; i++) {
			vallige[i] = i;
		}
		if (IS(mid)) {
			r = mid;
		}
		else {
			l= mid;
		}
	}
	if (r == 100005)
		cout << -1 ;
	else
		cout << r ;


	return 0;
}