import java.util.*;

public class Main {

	public static void main(String[] args) {
		// TODO 自動生成されたメソッド・スタブ
		Scanner sc = new Scanner(System.in);
		int a = sc.nextInt();
		int b = sc.nextInt();
		int c = sc.nextInt();
		int d;
		if(a == b && b == c) {
			d = a;
		} else if(a == b) {
			d = c;
		} else if(a == c) {
			d = b;
		} else if(b == c) {
			d = a;
		} else {
			d = 6 - (a + b + c);
		}
		System.out.println(d);
	}
}