import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {
	public static void main(String[] args) {
		BufferedReader buff = new BufferedReader(new InputStreamReader(System.in));

		try {
			String[] box = buff.readLine().split(" ");
			long[] f = new long[2];
			f[0] = Long.parseLong(box[0]);
			f[1] = Long.parseLong(box[1]);
			int n = Integer.parseInt(box[2]);
			if (n < 2) {
				System.out.println(f[n]);
				return;
			}
			int now = 1;
			while (now++ < n) {
				long w = f[0]^ f[1];
				f[0] = f[1];
				f[1] = w;
			}
			System.out.println(f[1]);

		} catch (NumberFormatException e) {
			e.getStackTrace();
		} catch (IOException e) {
			e.getStackTrace();
		}
	}
}