#include <bits/stdc++.h>
using namespace std;
int a[101];
int main(int argc, char *argv[]) {
  int n, b, s = 0, s1 = 0;
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> b;
    a[b]++;
  }
  for (int i = 1; i <= 100; i++) {
    if (a[i] >= 4) {
      s += a[i] / 4;
      a[i] -= 4 * (a[i] / 4);
    }
  }
  for (int i = 1; i <= 100; i++) {
    if (a[i] >= 2) {
      s1++;
    }
  }
  cout << s + s1 / 2;
  return EXIT_SUCCESS;
}
