#include <bits/stdc++.h>
using namespace std;
int main() {
  int mas[101] = {0};
  int n, a;
  int k = 0;
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> a;
    mas[a] += 1;
  }
  for (int i = 1; i <= 100; i++) {
    k += mas[i] / 2;
  }
  cout << k / 2;
  return 0;
}
