import java.util.Scanner;

public class No64 {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long F0 = sc.nextLong();
		long F1 = sc.nextLong();
		long N = sc.nextLong();
		long Fn = F0 ^ F1;
		long Fn1 = F1;
		long Fn2 = F0;
		
		for(int i = 3;i <= N;i++) {
			Fn2 = Fn1;
			Fn1 = Fn;
			Fn = Fn1 ^ Fn2;
		}
		
		if(N == 0) {
			System.out.println(F0);
		}else if(N == 1) {
			System.out.println(F1);
		}else {
			System.out.println(Fn);
		}
	}
}