import java.util.*;

class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		boolean[] vis = new boolean[10];
		for (int i = 0; i < 9; ++i) {
			int b = sc.nextInt() - 1;
			vis[b] = true;
		}
		for (int i = 0; i < 10; ++i) {
			if (!vis[i]) {
				System.out.println(i + 1);
			}
		}
	}
}