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