#include <bits/stdc++.h>
using namespace std;
int main() {
  const int LIMITE = 100;
  int numPalos;
  cin >> numPalos;
  int arr[LIMITE + 1] = {0};
  int temp = 0, total = 0;
  for (int k = 0; k < numPalos; k++) {
    cin >> temp;
    ++arr[temp];
  }
  for (int k = 0; k <= LIMITE; k++) {
    total += arr[k] / 2;
  }
  total /= 2;
  printf("%d\n", total);
  return 0;
}
