#include <bits/stdc++.h>
using namespace std;
const int MAXN1 = 10002;
const int MAXN2 = 10002;
const int MAXM = 100002;
int n1, n2, edges, last[MAXN1], pre[MAXM], head[MAXM];
int matching[MAXN2], dist[MAXN1], Q[MAXN1];
bool used[MAXN1], vis[MAXN1];
void init(int _n1, int _n2) {
  n1 = _n1;
  n2 = _n2;
  edges = 0;
  fill(last, last + n1, -1);
}
void addEdge(int u, int v) {
  head[edges] = v;
  pre[edges] = last[u];
  last[u] = edges++;
}
void bfs() {
  fill(dist, dist + n1, -1);
  int sizeQ = 0;
  for (int u = 0; u < n1; ++u) {
    if (!used[u]) {
      Q[sizeQ++] = u;
      dist[u] = 0;
    }
  }
  for (int i = 0; i < sizeQ; i++) {
    int u1 = Q[i];
    for (int e = last[u1]; e >= 0; e = pre[e]) {
      int u2 = matching[head[e]];
      if (u2 >= 0 && dist[u2] < 0) {
        dist[u2] = dist[u1] + 1;
        Q[sizeQ++] = u2;
      }
    }
  }
}
bool dfs(int u1) {
  vis[u1] = true;
  for (int e = last[u1]; e >= 0; e = pre[e]) {
    int v = head[e];
    int u2 = matching[v];
    if (u2 < 0 || !vis[u2] && dist[u2] == dist[u1] + 1 && dfs(u2)) {
      matching[v] = u1;
      used[u1] = true;
      return true;
    }
  }
  return false;
}
int maxMatching() {
  fill(used, used + n1, false);
  fill(matching, matching + n2, -1);
  for (int res = 0;;) {
    bfs();
    fill(vis, vis + n1, false);
    int f = 0;
    for (int u = 0; u < n1; ++u)
      if (!used[u] && dfs(u)) ++f;
    if (!f) return res;
    res += f;
  }
}
std::vector<pair<pair<int, int>, int>> v;
int main() {
  int i, n, m;
  cin >> n >> m;
  for (int i = 0; i < m; i++) {
    int x, y, w;
    cin >> x >> y >> w;
    v.push_back({{x, y}, w});
  }
  int lo = 0, hi = 1e9 + 2, ans = 1e9 + 2;
  while (lo <= hi) {
    int mid = lo + (hi - lo) / 2;
    memset(last, 0, sizeof(last));
    memset(pre, 0, sizeof(pre));
    memset(head, 0, sizeof(head));
    memset(matching, 0, sizeof(matching));
    memset(dist, 0, sizeof(dist));
    memset(Q, 0, sizeof(Q));
    memset(used, 0, sizeof(used));
    memset(vis, 0, sizeof(vis));
    init(n + 1, n + 1);
    for (int i = 0; i < m; i++) {
      if (v[i].second <= mid) {
        addEdge(v[i].first.first, v[i].first.second);
      }
    }
    int z = maxMatching();
    if (z == n) {
      ans = mid;
      hi = mid - 1;
    } else {
      lo = mid + 1;
    }
  }
  if (ans == 1e9 + 2)
    cout << -1;
  else
    cout << ans;
}
