#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int, int>;
template <typename... T>
void rd(T&... args) {
  ((cin >> args), ...);
}
template <typename... T>
void wr(T... args) {
  ((cout << args << " "), ...);
  cout << endl;
}
struct Dinic {
  struct Edge {
    int from, to, cap, flow;
    Edge(int u, int v, int c, int f) : from(u), to(v), cap(c), flow(f) {}
  };
  int n, s, t;
  vector<Edge> edges;
  vector<vector<int>> g;
  vector<int> d, cur;
  vector<int> vis;
  Dinic(int _n) : n(_n), g(n), d(n), cur(n), vis(n) { edges.clear(); }
  void init(int n) {
    for (int i = 0; i < n; i++) g[i].clear();
    edges.clear();
  }
  void AddEdge(int from, int to, int cap) {
    edges.push_back(Edge(from, to, cap, 0));
    edges.push_back(Edge(to, from, 0, 0));
    int m = (int)edges.size();
    g[from].push_back(m - 2);
    g[to].push_back(m - 1);
  }
  bool BFS() {
    fill(vis.begin(), vis.end(), 0);
    queue<int> Q;
    Q.push(s);
    d[s] = 0;
    vis[s] = 1;
    while (!Q.empty()) {
      int x = Q.front();
      Q.pop();
      for (int i = 0; i < (int)g[x].size(); i++) {
        Edge& e = edges[g[x][i]];
        if (!vis[e.to] && e.cap > e.flow) {
          vis[e.to] = 1;
          d[e.to] = d[x] + 1;
          Q.push(e.to);
        }
      }
    }
    return vis[t];
  }
  int DFS(int x, int a) {
    if (x == t || a == 0) return a;
    int flow = 0, f;
    for (int& i = cur[x]; i < (int)g[x].size(); i++) {
      Edge& e = edges[g[x][i]];
      if (d[x] + 1 == d[e.to] && (f = DFS(e.to, min(a, e.cap - e.flow))) > 0) {
        e.flow += f;
        edges[g[x][i] ^ 1].flow -= f;
        flow += f;
        a -= f;
        if (a == 0) break;
      }
    }
    return flow;
  }
  int Maxflow(int s, int t) {
    this->s = s;
    this->t = t;
    int flow = 0;
    while (BFS()) {
      const int INF = 1e9;
      fill(cur.begin(), cur.end(), 0);
      flow += DFS(s, INF);
    }
    return flow;
  }
};
int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int n, m;
  cin >> n >> m;
  vector<tuple<int, int, int>> a(m);
  for (auto& [d, u, v] : a) cin >> u >> v >> d;
  sort((a).begin(), (a).end());
  int l = 0, r = m - 1;
  Dinic dinic(2 * n + 2);
  while (l <= r) {
    dinic.init(2 * n + 2);
    int mid = (l + r) / 2;
    for (int i = 1; i <= n; i++) {
      dinic.AddEdge(0, i, 1);
      dinic.AddEdge(i + n, 2 * n + 1, 1);
    }
    for (int i = 0; i <= mid; i++) {
      auto [d, u, v] = a[i];
      dinic.AddEdge(u, n + v, 1);
    }
    int flow = dinic.Maxflow(0, 2 * n + 1);
    if (flow == n)
      r = mid - 1;
    else
      l = mid + 1;
  }
  cout << (l < m ? get<0>(a[l]) : -1);
  return 0;
}
