import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Scanner;

/**
 * PairedSocks
 */
public class PairedSocks {
  public static void main(String[] args) {

    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int[] randSocks = new int[n];
    for (int i = 0; i < randSocks.length; i++) {
      randSocks[i] = sc.nextInt();
    }
    sc.close();
    int pairCounted = pairingSocks(n, randSocks);
    System.out.println(pairCounted);
  }

  public static int pairingSocks(int n, int[] randSocks) {
    int socks = 0;
    Map<Integer, Integer> pairCount = new HashMap<>();
    // we are gonna go through the array of integer and check if there is 2 paires
    for (int x : randSocks) {
      System.out.print(x + "\t");
      pairCount.put(x, pairCount.getOrDefault(x, 0) + 1);
    }
    // count how many paires there is and return the sum.
    System.out.println("\n");
    for (int c : pairCount.values()) {
      socks = socks + c / 2;
    }
    return socks;
  }

}