#include <bits/stdc++.h>
using namespace std;
template <class T1, class T2>
ostream &operator<<(ostream &os, pair<T1, T2> &p);
template <class T>
ostream &operator<<(ostream &os, vector<T> &v);
template <class T>
ostream &operator<<(ostream &os, set<T> &v);
template <class T1, class T2>
ostream &operator<<(ostream &os, map<T1, T2> &v);
const int N = 1e5 + 5;
const long long mod = 1e9 + 7;
struct FlowEdge {
  int v, u;
  long long cap, flow = 0;
  FlowEdge(int v, int u, long long cap) : v(v), u(u), cap(cap) {}
};
struct Dinic {
  const long long flow_inf = 1e18;
  vector<FlowEdge> edges;
  vector<vector<int> > adj;
  int n, m = 0;
  int s, t;
  vector<int> level, ptr;
  queue<int> q;
  Dinic(int n, int s, int t) : n(n), s(s), t(t) {
    adj.resize(n);
    level.resize(n);
    ptr.resize(n);
  }
  Dinic(int n) {
    this->n = n;
    adj.resize(n);
    level.resize(n);
    ptr.resize(n);
  }
  void set_src_dest(int s, int t) {
    this->s = s;
    this->t = t;
  }
  void add_edge(int v, int u, long long cap) {
    edges.emplace_back(v, u, cap);
    edges.emplace_back(u, v, 0);
    adj[v].push_back(m);
    adj[u].push_back(m + 1);
    m += 2;
  }
  bool bfs() {
    while (!q.empty()) {
      int v = q.front();
      q.pop();
      for (int id : adj[v]) {
        if (edges[id].cap - edges[id].flow < 1) continue;
        if (level[edges[id].u] != -1) continue;
        level[edges[id].u] = level[v] + 1;
        q.push(edges[id].u);
      }
    }
    return level[t] != -1;
  }
  long long dfs(int v, long long pushed) {
    if (pushed == 0) return 0;
    if (v == t) return pushed;
    for (int &cid = ptr[v]; cid < (int)adj[v].size(); cid++) {
      int id = adj[v][cid];
      int u = edges[id].u;
      if (level[v] + 1 != level[u] || edges[id].cap - edges[id].flow < 1)
        continue;
      long long tr = dfs(u, min(pushed, edges[id].cap - edges[id].flow));
      if (tr == 0) continue;
      edges[id].flow += tr;
      edges[id ^ 1].flow -= tr;
      return tr;
    }
    return 0;
  }
  long long flow() {
    long long f = 0;
    while (true) {
      fill(level.begin(), level.end(), -1);
      level[s] = 0;
      q.push(s);
      if (!bfs()) break;
      fill(ptr.begin(), ptr.end(), 0);
      while (long long pushed = dfs(s, flow_inf)) {
        f += pushed;
      }
    }
    return f;
  }
};
int n, m;
vector<pair<pair<int, int>, int> > v;
bool check(int val) {
  Dinic d(n + n + 2, 0, n + n + 1);
  for (auto &it : v) {
    if (it.second <= val) {
      d.add_edge(it.first.first, n + it.first.second, 1);
    }
  }
  for (int i = 1; i <= n; i++) {
    d.add_edge(0, i, 1);
    d.add_edge(n + i, n + n + 1, 1);
  }
  int f = (int)d.flow();
  return f >= n;
}
void TEST_CASES(int cas) {
  cin >> n >> m;
  int low = 1e9, high = 0;
  v.resize(m);
  for (int i = 0; i < m; i++) {
    cin >> v[i].first.first >> v[i].first.second >> v[i].second;
    low = min(low, v[i].second);
    high = max(high, v[i].second);
  }
  int ans = -1;
  while (low <= high) {
    int mid = (low + high) / 2;
    if (check(mid)) {
      ans = mid;
      high = mid - 1;
    } else {
      low = mid + 1;
    }
  }
  cout << ans << "\n";
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  int t = 1, cas = 0;
  while (t--) {
    TEST_CASES(++cas);
  }
  return 0;
}
template <class T1, class T2>
ostream &operator<<(ostream &os, pair<T1, T2> &p) {
  os << "{" << p.first << ", " << p.second << "} ";
  return os;
}
template <class T>
ostream &operator<<(ostream &os, vector<T> &v) {
  os << "[ ";
  for (int i = 0; i < v.size(); i++) {
    os << v[i] << " ";
  }
  os << " ]";
  return os;
}
template <class T>
ostream &operator<<(ostream &os, set<T> &v) {
  os << "[ ";
  for (T i : v) {
    os << i << " ";
  }
  os << " ]";
  return os;
}
template <class T1, class T2>
ostream &operator<<(ostream &os, map<T1, T2> &v) {
  for (auto i : v) {
    os << "Key : " << i.first << " , Value : " << i.second << endl;
  }
  return os;
}
