import java.util.*;

public class Main {
	public static void main (String[] args) {
		Scanner sc = new Scanner(System.in);
		long[] arr = new long[3];
		arr[0] = sc.nextLong();
		arr[1] = sc.nextLong();
		int n = (int)(sc.nextLong() % 3);
		arr[2] = arr[0] ^ arr[1];
		System.out.println(arr[n]);
	}
}