#include <bits/stdc++.h>
using namespace std;
const long long mod = 1e9 + 7;
const int N = 1e6 + 6;
struct BipartiteMatcher {
  vector<vector<int>> G;
  vector<int> L, R, Viz;
  BipartiteMatcher(int n, int m) : G(n), L(n, -1), R(m, -1), Viz(n) {}
  void AddEdge(int a, int b) { G[a].push_back(b); }
  bool Match(int node) {
    if (Viz[node]) return false;
    Viz[node] = true;
    for (auto vec : G[node]) {
      if (R[vec] == -1) {
        L[node] = vec;
        R[vec] = node;
        return true;
      }
    }
    for (auto vec : G[node]) {
      if (Match(R[vec])) {
        L[node] = vec;
        R[vec] = node;
        return true;
      }
    }
    return false;
  }
  int Solve() {
    int ok = true;
    while (ok--) {
      fill(Viz.begin(), Viz.end(), 0);
      for (int i = 0; i < (int)L.size(); ++i)
        if (L[i] == -1) ok |= Match(i);
    }
    int ret = 0;
    for (int i = 0; i < (int)L.size(); ++i) ret += (L[i] != -1);
    return ret;
  }
};
struct edge {
  int u, v, w;
};
vector<edge> g;
int n, m;
bool ch(int x) {
  BipartiteMatcher bm(n + 1, n + 1);
  for (int i = 0; i < m; i++) {
    if (g[i].w <= x) {
      bm.AddEdge(g[i].u, g[i].v);
    }
  }
  int ret = bm.Solve();
  if (ret == n) return true;
  return false;
}
void solve() {
  cin >> n >> m;
  int mn = 1e9 + 1;
  int mx = 0;
  for (int i = 1; i <= m; i++) {
    edge d;
    cin >> d.u >> d.v >> d.w;
    mn = min(mn, d.w);
    mx = max(mx, d.w);
    g.push_back(d);
  }
  int st = mn;
  int en = mx;
  if (!ch(en)) {
    cout << -1 << endl;
    return;
  }
  if (ch(st)) {
    cout << st << endl;
    return;
  }
  while (st <= en) {
    int mid = (st + en) / 2;
    if (ch(mid)) {
      en = mid - 1;
    } else {
      st = mid + 1;
    }
  }
  cout << st << endl;
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int t = 1;
  while (t--) {
    solve();
  }
  return 0;
}
