#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, ai, nb = 0;
  map<int, int> dict;
  map<int, int>::iterator it;
  cin >> n;
  int i = 0;
  while (i < n) {
    cin >> ai;
    dict[ai]++;
    i++;
  }
  for (it = dict.begin(); it != dict.end(); it++) {
    while ((it->second) > 1) {
      it->second = (it->second) - 2;
      nb++;
    }
  }
  cout << (nb / 2);
  return 0;
}
