#include <bits/stdc++.h>
using namespace std;
const int INF = 1e9 + 7;
const int N = 3e5 + 5;
const int M = 3e6 + 5;
int n, m, s, t, maxflow = 0, lowflow;
struct node {
  int to, w, next;
} edge[M];
int head[N], cnt = 1, dep[N], inque[N], cur[N];
void add(int u, int v, int w) {
  edge[++cnt].next = head[u];
  edge[cnt].to = v;
  edge[cnt].w = w;
  head[u] = cnt;
}
struct Maxflow {
  bool bfs() {
    queue<int> q;
    memset(dep, -1, sizeof dep);
    dep[s] = 0;
    q.push(s);
    while (!q.empty()) {
      int u = q.front();
      q.pop();
      inque[u] = 0;
      for (int i = head[u]; i; i = edge[i].next) {
        int v = edge[i].to, w = edge[i].w;
        if (dep[v] == -1 && w) {
          dep[v] = dep[u] + 1;
          q.push(v);
        }
      }
    }
    return dep[t] != -1;
  }
  int dfs(int u, int flow) {
    if (u == t) {
      return flow;
    }
    int rlow = 0, used = 0;
    for (int i = cur[u]; i; i = edge[i].next) {
      int v = edge[i].to, w = edge[i].w;
      if (w && dep[v] == dep[u] + 1) {
        if (rlow = dfs(v, min(flow, w))) {
          used += rlow;
          flow -= rlow;
          edge[i].w -= rlow;
          edge[i ^ 1].w += rlow;
          if (flow == 0) break;
        }
      }
    }
    if (!used) dep[u] = -1;
    return used;
  }
  int Dinic() {
    maxflow = 0;
    while (bfs()) {
      for (int i = 0; i <= t; i++) cur[i] = head[i];
      maxflow += dfs(s, INF);
    }
    return maxflow;
  }
  void init() {
    cnt = 1;
    memset(head, 0, sizeof head);
  }
  void addedge(int u, int v, int w) {
    add(u, v, w);
    add(v, u, 0);
  }
} ac;
int u[N], w[N], v[N];
bool judge(int mid) {
  ac.init();
  s = 0, t = n * 2 + 1;
  for (int i = 1; i <= m; i++) {
    if (w[i] <= mid) ac.addedge(u[i], v[i] + n, 1);
  }
  for (int i = 1; i <= n; i++) ac.addedge(s, i, 1), ac.addedge(i + n, t, 1);
  ac.Dinic();
  return maxflow == n;
}
int main() {
  scanf("%d%d", &n, &m);
  for (int i = 1; i <= m; i++) {
    scanf("%d%d%d", &u[i], &v[i], &w[i]);
  }
  int ans = -1;
  int l = 1, r = 1e9;
  while (l <= r) {
    int mid = (l + r) / 2;
    if (judge(mid))
      ans = mid, r = mid - 1;
    else
      l = mid + 1;
  }
  cout << ans << endl;
}
