#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, i, x, ans, tmp;
  multiset<int> mys, s;
  multiset<int>::iterator it;
  while (cin >> n) {
    mys.clear(), s.clear();
    for (i = 0; i < n; ++i) {
      cin >> x;
      mys.insert(x);
    }
    for (it = mys.begin(); it != mys.end();) {
      tmp = mys.count(*it);
      if (tmp % 2) tmp -= 1;
      if (tmp >= 2) s.insert(tmp);
      it = mys.upper_bound(*it);
    }
    ans = 0;
    for (it = s.begin(); it != s.end(); ++it) ans += *it;
    cout << ans / 4 << endl;
  }
}
