#include <bits/stdc++.h>
using namespace std;
int a[110], n;
int main() {
  int i, j;
  cin >> n;
  for (i = 0; i < n; i++) cin >> a[i];
  if (n < 4)
    cout << 0 << endl;
  else {
    sort(a, a + n);
    int ct = 0;
    int t = 1;
    for (i = 1; i < n; i++) {
      if (a[i] != a[i - 1]) {
        ct += t / 2;
        t = 0;
      }
      t++;
    }
    ct += t / 2;
    cout << ct / 2 << endl;
  }
  return 0;
}
