#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main()
{
  int n;
  cin >> n;
  vector<int> cnt(n);
  for (int i = 0; i < n; ++i)
  {
    int a;
    cin >> a;
    --a;
    ++cnt[a];
  }
  int ans = 0;
  for (int i = 0; i < n; ++i) ans += cnt[i] / 2;
  cout << ans << endl;
}