#include <bits/stdc++.h>
using namespace std;
struct bipartite_graph {
  int n, m;
  vector<int> match, level, not_match;
  vector<vector<int>> adj;
  bool found;
  void init(int _n, int _m) {
    n = _n;
    m = _m;
    match.assign(m, -1);
    level.resize(m);
    adj.assign(n, vector<int>());
    not_match.resize(n);
    for (int i = 0; i < n; i++) not_match[i] = i;
  }
  void add(int u, int v) { adj[u].push_back(v); }
  bool bfs() {
    for (int i = 0; i < m; i++) level[i] = 0;
    queue<int> Q;
    for (auto& x : not_match) {
      if (x == -1) continue;
      for (auto& y : adj[x]) {
        if (!level[y]) {
          level[y] = 1;
          Q.push(y);
        }
      }
    }
    while (!Q.empty()) {
      int cur = Q.front();
      Q.pop();
      int x = match[cur];
      if (x == -1) return true;
      for (auto& y : adj[x]) {
        if (!level[y]) {
          level[y] = level[cur] + 1;
          Q.push(y);
        }
      }
    }
    return false;
  }
  void dfs(int x, int lv) {
    for (auto& y : adj[x]) {
      if (level[y] == lv + 1) {
        level[y] = 0;
        if (match[y] == -1)
          found = true;
        else
          dfs(match[y], lv + 1);
        if (found) {
          match[y] = x;
          return;
        }
      }
    }
  }
  int maximum_matching() {
    int res = 0;
    while (bfs()) {
      for (int i = not_match.size() - 1; i >= 0; i--) {
        if (not_match[i] == -1) continue;
        found = false;
        dfs(not_match[i], 0);
        if (found) {
          res++;
          not_match[i] = -1;
        }
      }
    }
    return res;
  }
} G;
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  int n, m;
  cin >> n >> m;
  vector<tuple<int, int, int>> edges;
  for (int i = 0; i < m; i++) {
    int u, v, w;
    cin >> u >> v >> w;
    --u;
    --v;
    edges.emplace_back(w, u, v);
  }
  sort(edges.begin(), edges.end());
  auto test = [&](int val) {
    G.init(n, n);
    for (auto& x : edges) {
      if (get<0>(x) > val) break;
      G.add(get<1>(x), get<2>(x));
    }
    return (G.maximum_matching() == n);
  };
  int l = 0, r = m - 1;
  while (l <= r) {
    int mid = l + r >> 1;
    if (test(get<0>(edges[mid])))
      r = mid - 1;
    else
      l = mid + 1;
  }
  if (l == m)
    cout << "-1";
  else
    cout << get<0>(edges[l]);
}
