#include <bits/stdc++.h>
using namespace std;
int main() {
  map<int, int> m;
  int n, a, sum(0);
  cin >> n;
  while (n--) {
    cin >> a;
    m[a]++;
  }
  for (auto i : m) {
    if (i.second >= 2) {
      sum += (i.second / 2);
    }
  }
  cout << sum / 2 << endl;
  return 0;
}
