#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, sti[101], i, x, ans;
  cin >> n;
  memset(sti, 0, sizeof(sti));
  for (i = 1; i <= n; i++) {
    cin >> x;
    sti[x]++;
  }
  ans = 0;
  for (i = 1; i <= 100; i++) {
    ans += 2 * (sti[i] / 4);
    sti[i] %= 4;
    ans += sti[i] / 2;
  }
  cout << ans / 2 << endl;
  return 0;
}
