import java.util.Scanner;

class Yuki64 {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int a = sc.nextInt();
    int b = sc.nextInt();
    int n = sc.nextInt();
    int x = 0;
    if(n>=2){
      x = fib(b,a,n);
    } else if(n==0){
      x = a;
    } else if(n==1){
      x = b;
    }
    System.out.println(x);
  }

  private static int fib(int b,int a,int n) {
    int c = b^a;
    n-=1;
    if(n==1) return c;
    return fib(c,b,n);
  }
}