import java.util.*;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    long f0 = sc.nextLong();
    long f1 = sc.nextLong();
    long f2 = f0 ^ f1;
    long ans = f0;
    long N = sc.nextLong();
    if(N % 3 == 1) ans = f1;
    if(N % 3 == 2) ans = f2;
    System.out.println(ans);
  }
}