#include <bits/stdc++.h>
using namespace std;
int main() {
  int in, n, res, arr[110] = {0}, i;
  scanf(" %d", &n);
  for (i = 1; i <= n; i++) {
    scanf(" %d", &in);
    arr[in]++;
  }
  for (i = 0, res = 0; i <= 100; i++) {
    res += arr[i] / 2;
  }
  printf("%d\n", res / 2);
  return 0;
}
