#include <bits/stdc++.h>
int main() {
  std::ios_base::sync_with_stdio(false);
  std::cin.tie(0);
  std::cout.tie(0);
  std::cerr.tie(0);
  int n;
  std::cin >> n;
  std::vector<int> cnt(1 + 100);
  while (n--) {
    int a;
    std::cin >> a;
    cnt[a]++;
  }
  int answ = 0;
  for (int i = 1; i <= 100; ++i) {
    while (cnt[i] >= 4) {
      cnt[i] -= 4;
      answ++;
    }
  }
  for (int i = 1; i <= 100; ++i) {
    for (int j = i + 1; j <= 100; ++j) {
      if (cnt[i] >= 2 && cnt[j] >= 2) {
        cnt[i] -= 2;
        cnt[j] -= 2;
        answ++;
      }
    }
  }
  std::cout << answ;
  return 0;
}
