#include <bits/stdc++.h>
using namespace std;

int main() {
  int N;
  cin >> N;
  map<int, int> MA;
  while (cin >> N) MA[N]++;
  int ans = 0, rem = 0;
  for (auto [a, b] : MA) ans += b / 2, rem += b % 2;
  cout << ans + rem / 4 << "\n";
}