#include <bits/stdc++.h>
using namespace std;
const int N = 2e5 + 10;
const int M = (1e5 + 10 + N) * 2;
const int inf = 0x3f3f3f3f;
int n, m, S, T;
struct node {
  int u, v, w;
} Edge[N];
bool cmp(node &a, node &b) { return a.w < b.w; }
int h[N], tot, e[M], f[M], ne[M];
int d[N], cur[N];
void add(int u, int v, int w) {
  e[tot] = v, f[tot] = w, ne[tot] = h[u], h[u] = tot++;
  e[tot] = u, f[tot] = 0, ne[tot] = h[v], h[v] = tot++;
}
bool bfs() {
  queue<int> q;
  q.push(S);
  memset(d, -1, sizeof d);
  d[S] = 0;
  cur[S] = h[S];
  while (!q.empty()) {
    int u = q.front();
    q.pop();
    for (int i = h[u]; ~i; i = ne[i]) {
      int v = e[i];
      if (d[v] == -1 && f[i]) {
        d[v] = d[u] + 1;
        cur[v] = h[v];
        if (v == T) return true;
        q.push(v);
      }
    }
  }
  return false;
}
int dfs(int u, int limit) {
  if (u == T) return limit;
  int flow = 0;
  for (int i = cur[u]; ~i && flow < limit; i = ne[i]) {
    cur[u] = i;
    int v = e[i];
    if (d[v] == d[u] + 1 && f[i]) {
      int t = dfs(v, min(f[i], limit - flow));
      flow += t;
      f[i] -= t;
      f[i ^ 1] += t;
    }
  }
  return flow;
}
int dinic() {
  int flow, res = 0;
  while (bfs()) {
    while (flow = dfs(S, inf)) res += flow;
  }
  return res;
}
bool check(int mid) {
  S = 0, T = 2 * n + 1;
  for (int i = 0; i <= T; i++) h[i] = -1;
  tot = 0;
  for (int i = 1; i <= n; i++) add(S, i, 1);
  for (int j = 1; j <= n; j++) add(n + j, T, 1);
  for (int i = 1; i <= m; i++) {
    if (Edge[i].w > mid) break;
    add(Edge[i].u, n + Edge[i].v, Edge[i].w);
  }
  return dinic() == n;
}
int main() {
  scanf("%d%d", &n, &m);
  for (int i = 1; i <= m; i++)
    scanf("%d%d%d", &Edge[i].u, &Edge[i].v, &Edge[i].w);
  sort(Edge + 1, Edge + 1 + m, cmp);
  int l = 1, r = Edge[m].w;
  int ans = -1;
  while (l <= r) {
    int mid = (l + r) / 2;
    if (check(mid)) {
      r = mid - 1;
      ans = mid;
    } else
      l = mid + 1;
  }
  printf("%d\n", ans);
  return 0;
}
