#include <bits/stdc++.h>
using namespace std;
const long long N = 100 * 1000 + 100;
vector<pair<long long, long long> > G[N];
long long match[N], dist[N];
long long n, mid;
bool bfs() {
  queue<long long> q;
  for (long long i = 1; i <= n; i++) {
    if (match[i] == 0) {
      dist[i] = 0;
      q.push(i);
    } else
      dist[i] = 2147483647;
  }
  dist[0] = 2147483647;
  while (!q.empty()) {
    long long u = q.front();
    q.pop();
    if (u == 0) continue;
    for (long long i = 0; i < (long long)G[u].size(); i++) {
      if (G[u][i].second > mid) continue;
      long long v = G[u][i].first;
      if (dist[match[v]] == 2147483647) {
        dist[match[v]] = dist[u] + 1;
        q.push(match[v]);
      }
    }
  }
  return dist[0] != 2147483647;
}
bool dfs(long long u) {
  if (u != 0) {
    for (long long i = 0; i < (long long)G[u].size(); i++) {
      if (G[u][i].second > mid) continue;
      long long v = G[u][i].first;
      if (dist[match[v]] == dist[u] + 1) {
        if (dfs(match[v])) {
          match[v] = u;
          match[u] = v;
          return true;
        }
      }
    }
    dist[u] = 2147483647;
    return false;
  }
  return true;
}
long long hopcroft_karp() {
  for (long long i = 0; i < N; i++) match[i] = dist[i] = 0;
  long long matching = 0;
  while (bfs()) {
    for (long long i = 1; i <= n; i++) {
      if (match[i] == 0 && dfs(i)) matching++;
    }
  }
  return matching;
}
void solve() {
  long long m;
  cin >> n >> m;
  while (m--) {
    long long a, b, c;
    cin >> a >> b >> c;
    G[a].push_back({b + n, c});
  }
  long long low = 0, high = 1000 * 1000 * 1000;
  long long best = -1;
  while (low <= high) {
    mid = (low + high) / 2;
    if (hopcroft_karp() == n) {
      high = mid - 1;
      best = mid;
    } else
      low = mid + 1;
  }
  cout << best << '\n';
}
int32_t main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  solve();
  return 0;
}
