import java.io.*; import java.math.*; import java.security.*; import java.text.*; import java.util.*; import java.util.concurrent.*; import java.util.regex.*; import java.util.Arrays; public class Solution { // Complete the sockMerchant function below. static int sockMerchant(int n, int[] ar) { Arrays.sort(ar); int pairs = 0; int match = 0; while (match < n - 1) { if (ar[match] == ar[match + 1]) { pairs++; match = match + 2; } else { match++; } } return pairs; } private static final Scanner scanner = new Scanner(System.in); public static void main(String[] args) throws IOException { BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(System.getenv("OUTPUT_PATH"))); int n = scanner.nextInt(); scanner.skip("(\r\n|[\n\r\u2028\u2029\u0085])?"); int[] ar = new int[n]; String[] arItems = scanner.nextLine().split(" "); scanner.skip("(\r\n|[\n\r\u2028\u2029\u0085])?"); for (int i = 0; i < n; i++) { int arItem = Integer.parseInt(arItems[i]); ar[i] = arItem; } int result = sockMerchant(n, ar); bufferedWriter.write(String.valueOf(result)); bufferedWriter.newLine(); bufferedWriter.close(); scanner.close(); } }