#include <bits/stdc++.h>
using namespace std;
int n, ans, dp[123];
int main() {
  cin >> n;
  for (int i = 0, a; i < n; i++) cin >> a, dp[a]++;
  for (int i = 0; i <= 100; i++) dp[i] /= 2, ans += dp[i];
  cout << ans / 2;
}
