import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner koko = new Scanner(System.in);
        long zero = koko.nextLong();
        long one = koko.nextLong();
        long n = koko.nextLong();
        if(n%3==0){
            System.out.println(zero);
        }else if(n%3==1){
            System.out.println(one);
        }else{
            String tz = Long.toBinaryString(zero);
            String to = Long.toBinaryString(one);
            int min = Math.min(tz.length(),to.length());
            int max = Math.max(tz.length(),to.length());
            char[] ans = new char[max];
            if(tz.length()>to.length()){
                for(int i=0; i<min; i++){
                    if(tz.charAt(max-1-i)==to.charAt(min-1-i)){
                        ans[max-1-i] = '0';
                    }else{
                        ans[max-1-i] = '1';
                    }
                }
                for(int i=0; i<max-min; i++){
                        ans[i] = tz.charAt(i);
                }
            }else if(tz.length()<to.length()){
                for(int i=0; i<min; i++){
                    if(tz.charAt(min-1-i)==to.charAt(max-1-i)){
                        ans[max-1-i] = '0';
                    }else{
                        ans[max-1-i] = '1';
                    }
                }
                for(int i=0; i<max-min; i++){
                        ans[i] = to.charAt(i);
                } 
            }else{
                for(int i=0; i<min; i++){
                    if(tz.charAt(min-1-i)==to.charAt(max-1-i)){
                        ans[max-1-i] = '0';
                    }else{
                        ans[max-1-i] = '1';
                    }
                }
            }
            String an = String.valueOf(ans);
            long a = Long.parseLong(an,2);
            System.out.println(a);
        }
    }
}