#include <bits/stdc++.h>
using namespace std;
const int maxn = 2e4 + 5;
struct Edge {
  int from, to, cap, flow;
};
struct Dinic {
  int n, m, s, t;
  vector<Edge> edges;
  vector<int> G[maxn];
  bool vis[maxn];
  int d[maxn];
  int cur[maxn];
  void ClearAll(int n) {
    this->n = n;
    for (int i = 0; i < n; i++) G[i].clear();
    edges.clear();
  }
  void ClearFlow() {
    for (int i = 0; i < edges.size(); i++) edges[i].flow = 0;
  }
  void AddEdge(int from, int to, int cap) {
    edges.push_back((Edge){from, to, cap, 0});
    edges.push_back((Edge){to, from, 0, 0});
    m = edges.size();
    G[from].push_back(m - 2);
    G[to].push_back(m - 1);
  }
  bool BFS() {
    memset(vis, 0, n * sizeof(vis[0]));
    queue<int> Q;
    Q.push(s);
    vis[s] = 1;
    d[s] = 0;
    while (!Q.empty()) {
      int x = Q.front();
      Q.pop();
      for (int i = 0; i < 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 < 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()) {
      memset(cur, 0, n * sizeof(cur[0]));
      flow += DFS(s, n + 1);
    }
    return flow;
  }
  vector<int> Mincut() {
    vector<int> ans;
    for (int i = 0; i < edges.size(); i++) {
      Edge& e = edges[i];
      if (vis[e.from] && !vis[e.to] && e.cap > 0) ans.push_back(i);
    }
    return ans;
  }
  void Reduce() {
    for (int i = 0; i < edges.size(); i++) edges[i].cap -= edges[i].flow;
  }
} solver;
const int N = 1e4 + 1;
struct Edge_ {
  int u, v, len;
  void read() { scanf("%d %d %d", &u, &v, &len); }
  bool operator<(const Edge_& r) const { return len < r.len; }
};
vector<Edge_> edges;
int n, m;
int main() {
  scanf("%d %d", &n, &m);
  vector<int> perm(n);
  for (int i = 0; i < n; ++i) perm[i] = i;
  srand(19950808ll);
  random_shuffle(perm.begin(), perm.end());
  edges.resize(m);
  for (auto& e : edges) e.read();
  for (auto& e : edges) e.u = perm[e.u - 1] + 1, e.v = perm[e.v - 1] + 1;
  sort(edges.begin(), edges.end());
  int ans = -1, l = 0, r = m - 1, mid;
  while (l <= r) {
    mid = (l + r) >> 1;
    solver.ClearAll(2 * n + 2);
    int src = 0, dest = 2 * n + 1;
    for (int i = 1; i <= n; ++i)
      solver.AddEdge(src, i, 1), solver.AddEdge(n + i, dest, 1);
    for (int i = 0; i <= mid; ++i) {
      const auto& e = edges[i];
      solver.AddEdge(e.u, e.v + n, 1);
    }
    if (solver.Maxflow(src, dest) == n) {
      ans = edges[mid].len;
      r = mid - 1;
    } else
      l = mid + 1;
  }
  printf("%d\n", ans);
}
