#include <bits/stdc++.h>
using namespace std;
int n;
int cnt[101];
void do_solve() {
  scanf("%d", &n);
  for (int i = 0; i < n; i++) {
    int t;
    scanf("%d", &t);
    cnt[t]++;
  }
  int s = 0;
  for (int i = 1; i <= 100; i++) s += cnt[i] / 2;
  cout << s / 2;
}
int main() {
  do_solve();
  return 0;
}
