#include <bits/stdc++.h>
using namespace std;
int n, k, a[105], p;
int main() {
  cin >> n;
  for (int i = 1; i <= n; i++) {
    cin >> k;
    a[k]++;
  }
  for (int i = 1; i <= 100; i++) {
    p += a[i] / 2;
  }
  cout << p / 2;
  return 0;
}
