#include <bits/stdc++.h>
using namespace std;
const int N = 1e4 + 5, INF = 1e9, NIL = 2e4 + 5;
int n, m;
vector<pair<int, int>> adj[2 * N];
int batas;
int matchU[2 * N], matchV[2 * N];
int dist[2 * N];
bool bfs() {
  queue<int> q;
  for (int i = (1); i <= (int)(n); i += (1)) {
    if (matchU[i] == NIL) {
      dist[i] = 0;
      q.push(i);
    } else {
      dist[i] = INF;
    }
  }
  dist[NIL] = INF;
  while (!q.empty()) {
    int u = q.front();
    q.pop();
    if (dist[u] < dist[NIL]) {
      for (auto it : adj[u]) {
        int v = it.first, w = it.second;
        if (w > batas) continue;
        if (dist[matchV[v]] == INF) {
          dist[matchV[v]] = dist[u] + 1;
          q.push(matchV[v]);
        }
      }
    }
  }
  return dist[NIL] != INF;
}
int dfs(int u) {
  if (u == NIL) return 1;
  for (auto it : adj[u]) {
    int v = it.first, w = it.second;
    if (w > batas) continue;
    if (dist[matchV[v]] == dist[u] + 1 && dfs(matchV[v])) {
      matchV[v] = u;
      matchU[u] = v;
      return 1;
    }
  }
  dist[u] = INF;
  return 0;
}
int mcbm() {
  int ret = 0;
  for (int i = (1); i <= (int)(n); i += (1)) matchU[i] = NIL;
  for (int i = (n + 1); i <= (int)(2 * n); i += (1)) matchV[i] = NIL;
  while (bfs()) {
    for (int i = (1); i <= (int)(n); i += (1))
      if (matchU[i] == NIL) {
        ret += dfs(i);
      }
  }
  return ret;
}
int main() {
  ios::sync_with_stdio(0);
  cin.tie(0);
  cin >> n >> m;
  for (int i = 0; i < (int)(m); i++) {
    int u, v, w;
    cin >> u >> v >> w;
    adj[u].push_back({v + n, w});
    adj[v + n].push_back({u, w});
  }
  int ans = -1;
  int l = 1, r = 1e9;
  while (l <= r) {
    int mid = (l + r) / 2;
    batas = mid;
    if (mcbm() == n)
      r = mid - 1, ans = mid;
    else
      l = mid + 1;
  }
  cout << ans << '\n';
  return 0;
}
