#include <bits/stdc++.h>
using namespace std;
using i64 = int64_t;
using ui64 = uint64_t;
template <class A, class B>
bool smin(A &x, B &&y) {
  if (y < x) {
    x = y;
    return true;
  }
  return false;
}
template <class A, class B>
bool smax(A &x, B &&y) {
  if (x < y) {
    x = y;
    return true;
  }
  return false;
}
class matching {
 public:
  vector<vector<int>> g;
  vector<int> pa;
  vector<int> pb;
  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);
    pb = 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 (pb[u] == -1) {
        pa[v] = u;
        pb[u] = v;
        return true;
      }
    }
    for (int u : g[v]) {
      if (was[pb[u]] != iter && dfs(pb[u])) {
        pa[v] = u;
        pb[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);
  }
};
int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int n, m;
  cin >> n >> m;
  vector<tuple<int, int, int>> edges(m);
  for (auto &[i, x, y] : edges) {
    cin >> x >> y >> i;
    --x, --y;
  }
  sort(edges.begin(), edges.end());
  auto can = [&](int mid) {
    matching match(n, n);
    for (int i = 0; i < mid; ++i) {
      match.add(get<1>(edges[i]), get<2>(edges[i]));
    }
    return match.solve() == n;
  };
  int l = 0;
  int r = m + 1;
  while (l + 1 < r) {
    int mid = (l + r) / 2;
    if (can(mid)) {
      r = mid;
    } else {
      l = mid;
    }
  }
  cout << (r > m ? -1 : get<0>(edges[r - 1])) << '\n';
  return 0;
}
