#include <bits/stdc++.h>
using namespace std;
int a[10010];
int n;
void conduct() {
  int i, cnt;
  for (i = 0; i < n; ++i) scanf("%d", &a[i]);
  sort(a, a + n);
  for (cnt = i = 0; i < n - 1; ++i)
    if (a[i] == a[i + 1]) {
      cnt++;
      i++;
    }
  printf("%d\n", cnt / 2);
}
int main() {
  while (scanf("%d", &n) != EOF) conduct();
  return 0;
}
