#include <bits/stdc++.h>
int main() {
  int32_t n;
  std::cin >> n;
  int32_t* sticks = new int32_t[n];
  for (int32_t i = 0; i < n; i++) std::cin >> sticks[i];
  std::sort(sticks, sticks + n);
  int32_t num_pairs = 0;
  bool available = true;
  for (int32_t i = 1; i < n; i++) {
    if (sticks[i] == sticks[i - 1] && available) {
      num_pairs++;
      available = false;
    } else {
      available = true;
    }
  }
  std::cout << num_pairs / 2;
  return 0;
}
