#include <bits/stdc++.h>
using namespace std;
class matching {
 public:
  vector<vector<int>> g;
  vector<int> pa;
  vector<int> push_back;
  vector<int> was;
  int n, m;
  int res;
  int iter;
  matching(int _n, int _m) : n(_n), m(_m) {
    assert(0 <= n && 0 <= m);
    pa = vector<int>(n, -1);
    push_back = vector<int>(m, -1);
    was = vector<int>(n, 0);
    g.resize(n);
    res = 0;
    iter = 0;
  }
  void add(int from, int to) {
    assert(0 <= from && from < n && 0 <= to && to < m);
    g[from].push_back(to);
  }
  bool dfs(int v) {
    was[v] = iter;
    for (int u : g[v]) {
      if (push_back[u] == -1) {
        pa[v] = u;
        push_back[u] = v;
        return true;
      }
    }
    for (int u : g[v]) {
      if (was[push_back[u]] != iter && dfs(push_back[u])) {
        pa[v] = u;
        push_back[u] = v;
        return true;
      }
    }
    return false;
  }
  int solve() {
    while (true) {
      iter++;
      int add = 0;
      for (int i = 0; i < n; i++) {
        if (pa[i] == -1 && dfs(i)) {
          add++;
        }
      }
      if (add == 0) {
        break;
      }
      res += add;
    }
    return res;
  }
  int run_one(int v) {
    if (pa[v] != -1) {
      return 0;
    }
    iter++;
    return (int)dfs(v);
  }
};
bool comp(const pair<int, pair<int, int>> &a,
          const pair<int, pair<int, int>> &b) {
  return a.second.second < b.second.second;
}
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  ;
  int t = 1;
  while (t--) {
    int n, m;
    cin >> n >> m;
    vector<pair<int, pair<int, int>>> roads;
    for (int i = 0; i < m; ++i) {
      int u, v, w;
      cin >> u >> v >> w;
      --u;
      --v;
      roads.push_back({u, {v, w}});
    }
    sort(roads.begin(), roads.end(), comp);
    int lo = 0, hi = roads[m - 1].second.second + 1;
    while (lo < hi) {
      int md = (lo + hi) >> 1;
      matching graph(n, n);
      for (auto it : roads) {
        if (it.second.second <= md)
          graph.add(it.first, it.second.first);
        else
          break;
      }
      int cnt = graph.solve();
      if (cnt < n) {
        lo = md + 1;
      } else
        hi = md;
    }
    if (hi == roads[m - 1].second.second + 1)
      cout << -1;
    else
      cout << hi;
  }
  return 0;
}
