#include <bits/stdc++.h>
using namespace std;
int counter[101], c;
int main() {
  int n;
  cin >> n;
  for (int i = 0; i < n; i++) {
    int a;
    cin >> a;
    counter[a]++;
  }
  for (int i = 0; i < 101; i++) c += counter[i] / 2;
  cout << c / 2;
  return 0;
}
