#include <bits/stdc++.h>
using namespace std;

const int N = 100010;

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

node a[N];
int n, m;
int f[N];

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

void bing(int x, int y)
{
    int a1 = find(x);
    int a2 = find(y);
    if (a1 != a2)
    {
        n--;
        f[x] = y;
    }
}

bool cmp(node x, node y)
{
    return x.t < y.t;
}

int main()
{
    scanf("%d%d", &n, &m);
    for (int i = 1; i <= n; i++)
        f[i] = i;
    for (int i = 1; i <= m; i++)
        scanf("%d%d%d", &a[i].x, &a[i].y, &a[i].t);

    sort(a + 1, a + 1 + m, cmp);

    for (int i = 1; i <= m; i++)
    {
        bing(a[i].x, a[i].y);
        if (n == 1)
        {
            printf("%d\n", a[i].t);
            return 0;
        }
    }

    printf("-1\n");

    return 0;
}