#include <bits/stdc++.h>
using namespace std;
int main(void) {
  int n;
  vector<int> a;
  cin >> n;
  a.resize(n);
  for (int i = 0; i < n; ++i) cin >> a[i];
  sort(a.begin(), a.end());
  int pair = 0;
  for (int i = 0; i < n - 1;)
    if (a[i] == a[i + 1]) {
      pair++;
      i += 2;
    } else
      i += 1;
  cout << int(pair / 2);
  return 0;
}
