#include <bits/stdc++.h>
using namespace std;
int main() {
  int a[110], n, i, j, cnt;
  while (cin >> n) {
    for (i = 0; i < n; i++) cin >> a[i];
    sort(a, a + n);
    i = 0;
    cnt = 0;
    while (i < n - 1) {
      if (a[i] == a[i + 1]) {
        cnt++;
        i += 2;
      } else
        i++;
    }
    cout << (cnt / 2) << endl;
  }
  return 0;
}
