import java.util.Scanner;

class Yuki64 {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    long a = sc.nextLong();
    long b = sc.nextLong();
    long c = a^b;
    long n = sc.nextLong();
    long x = 0;
    if(n%3==0){
      x = a;
    } else if(n%3==1){
      x = b;
    } else if(n%3==2){
      x = c;
    }
    System.out.println(x);
  }
}