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  missmphuog  đã bình luận lúc 7, Tháng 3, 2026, 9:05

  #include <bits/stdc++.h>
  using namespace std;
  
  #define ll long long
  #define ull unsigned long long
  #define ld long double
  
  #define pb push_back
  #define pf push_front
  #define fi first
  #define se second
  
  #define all(x) (x).begin(), (x).end()
  #define rall(x) (x).rbegin(), (x).rend()
  
  #define faster() ios::sync_with_stdio(false); cin.tie(nullptr);
  #define endl '\n'
  
  #define yes cout << "YES\n"
  #define no  cout << "NO\n"
  
  #define pii pair<int,int>
  #define pll pair<ll,ll>
  #define vi vector<int>
  #define vl vector<ll>
  const int maxn = 1e6;
  int a[maxn+10],n,d=0;
  int main() {
      faster();
      cin>>n;
      map<int,int> mp;
      for(int i=1;i<=n;i++) {
          cin>>a[i];
          mp[a[i]]++;
      }
      vi v;
      for(auto it:mp) {
          if(it.second>=3) {
              v.push_back(it.first);
          }
      }
      if(!v.empty()) cout<&lt;v[0];
      else cout<<-1;
      return 0;
  }