#include <bits/stdc++.h>
using namespace std;
int a[105];
int main() {
  int n;
  scanf("%d", &n);
  for (int i = 1; i <= n; ++i) scanf("%d", &a[0]), ++a[a[0]];
  int ans = 0;
  for (int i = 1; i <= 100; ++i) ans += a[i] / 2;
  printf("%d\n", ans / 2);
}
