import java.util.*;
 

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long n = sc.nextLong();
		long m=sc.nextLong();
		long l=sc.nextLong();
		if(l==1){
			System.out.println(m);
			return;
		}
		if(l==0){
			System.out.println(n);
			return;
		}
		for(int i=1;i<=l-1;i++){
			long temp=m;
			m^=n;
			n=temp;
		}
		System.out.println(m);
	}
}