#include <bits/stdc++.h>
using namespace std;
int arr[110];
int main() {
  int a, n, sum = 0, two = 0;
  vector<int> v;
  cin >> a;
  for (int i = 0; i < a; i++) {
    cin >> n;
    arr[n]++;
  }
  for (int i = 0; i < 110; i++) {
    if (arr[i] >= 4) {
      sum += (arr[i] / 4);
      arr[i] %= 4;
    }
  }
  for (int i = 0; i < 110; i++) {
    if (arr[i] >= 2) two++;
  }
  sum += (two / 2);
  cout << sum << endl;
  return 0;
}
