import java.util.*;

public class Test {
    public static void main(String[] args) {
        List list = new ArrayList<String>();
        for (int i = 0; i < 10; i++) {
            list.add(i + "");
        }

        for (Object e1 : list) {
            for (Object e2 : list) {
                if (e1.equals(e2)) {
                    list.remove(e1);
                    list.remove(e2);
                }
            }
        }
        System.out.println(list.size());
    }
}