import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        boolean[] f = new boolean[11];
        for (int i = 0; i != 9; i++) {
            f[sc.nextInt()] = true;
        }
        for (int i = 1; i != 11; i++) {
            if (!f[i]) {
                System.out.println(i);
            }
        }

        sc.close();

    }
}