#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, a[101], i, cash[101] = {0}, sum = 0, ans;
  scanf("%d", &n);
  for (i = 1; i <= n; i++) scanf("%d", &a[i]);
  for (i = 1; i <= n; i++) cash[a[i]]++;
  for (i = 1; i <= 100; i++) {
    if (cash[i] > 1) {
      if (cash[i] % 2 == 1)
        sum = sum + cash[i] - 1;
      else
        sum = sum + cash[i];
    }
  }
  ans = sum / 4;
  printf("%d", ans);
}
