#include <bits/stdc++.h>
using namespace std;
int a[101], n, i, k, c;
int main() {
  cin >> n;
  for (i = 0; i < n; i++) {
    cin >> k;
    a[k]++;
  }
  for (i = 0; i <= 100; i++) {
    a[i] = a[i] / 2;
    c = c + a[i];
  }
  cout << c / 2;
}
