#include <bits/stdc++.h>
using namespace std;
int n, x;
map<int, int> cnt;
int main() {
  cin >> n;
  for (int i = 0; i < n; i++) cin >> x, cnt[x]++;
  int ret = 0;
  for (int i = 1; i <= 100; i++) ret += (cnt[i] / 2);
  cout << ret / 2 << endl;
  return 0;
}
