/* -*- coding: utf-8 -*-
 *
 * 2851.cc:  No.2851 Make Pairs - yukicoder
 */

#include<cstdio>
#include<algorithm>

using namespace std;

/* constant */

const int MAX_N = 200000;

/* typedef */

/* global variables */

int as[MAX_N], cs[MAX_N];

/* subroutines */

/* main */

int main() {
  int n;
  scanf("%d", &n);
  for (int i = 0; i < n; i++) scanf("%d", as + i), as[i]--;
  
  for (int i = 0; i < n; i++) cs[as[i]]++;

  int sum = 0;
  for (int i = 0; i < n; i++) sum += (cs[i] >> 1);
  
  printf("%d\n", sum);
  
  return 0;
}