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