#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  cin >> N;
  vector<int> a(N);
  for (int i = 0; i < N; ++i) {
    scanf("%d", &a[i]);
  }
  sort(a.begin(), a.end());
  int res = 0;
  for (int i = 0; i <= N; ++i) {
    if (a[i] == a[i + 1]) {
      ++res;
      ++i;
    }
  }
  cout << res / 2 << endl;
  return 0;
}
