#include<iostream>
#include<algorithm>
using namespace std;

const int MAXN = 10005;
int f[MAXN];

struct node {
    int x, y, t;
};

bool cmp(node a, node b) {
    return a.t < b.t;
}

int find(int i) {
    if (f[i] != i) {
        f[i] = find(f[i]);
    }
    return f[i];
}

int main() {
    int n, m;
    cin >> n >> m;
    
    // 初始化并查集
    for (int i = 1; i <= n; i++) {
        f[i] = i;
    }
    
    // 读取边的信息
    node b[MAXN];
    for (int i = 1; i <= m; i++) {
        cin >> b[i].x >> b[i].y >> b[i].t;
    }
    
    // 按边的权重排序
    sort(b + 1, b + 1 + m, cmp);
    
    int num = 0, ans = 0;
    
    // Kruskal算法核心部分
    for (int i = 1; i <= m; i++) {
        int r1 = find(b[i].x);
        int r2 = find(b[i].y);
        
        if (r1 != r2) {
            f[r1] = r2;  // 合并两个集合
            num++;
            ans = max(ans, b[i].t);
            if (num == n - 1) break;  // 提前结束循环
        }
    }
    
    // 检查是否形成了最小生成树
    if (num != n - 1) {
        cout << -1;
    } else {
        cout << ans;
    }
    
    return 0;
}