import java.util.Scanner;
class N064{
	public static void main(String args[]){
		Scanner s = new Scanner(System.in);
		long f0 = s.nextLong();
		long f1 = s.nextLong();
		long n = s.nextLong();
		if(n % 3 == 0){
			System.out.println(f0);
		}else if(n % 3 == 1){
			System.out.println(f1);
		}else{
			System.out.println(f0 ^ f1);
		}
	}
}