import java.util.*;
import java.util.stream.Stream;
import java.time.*;
import java.time.format.*;

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();
        if(n%3 == 0) {
            System.out.println(f0);
        }else if(n%3 == 1) {
            System.out.println(f1);
        }else {
            System.out.println(f0 ^ f1);
        }
	}
}