import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        long f0_ans = scan.nextLong();
        long f1_ans = scan.nextLong();
        long n = scan.nextLong();
        if(n%3 == 0){
        	System.out.println(f0_ans);
        }else if(n%3 == 1){
        	System.out.println(f1_ans);
        }else{
        	System.out.println(n%3);
        }
    }
}