//No.64 XORフィボナッチ数列

import java.util.*;
import java.io.*;
import static java.util.Arrays.*;
import static java.lang.Math.*;

public class No64 {
    
    static final Scanner sc = new Scanner(System.in);
    static final PrintWriter out = new PrintWriter(System.out,false);

    static void solve() {
        long[] f = new long[3];
        f[0] = sc.nextLong();
        f[1] = sc.nextLong();
        long n = sc.nextLong();
        f[2] = f[0]^f[1];
        out.println(f[(int)(n%3)]);
    }

    public static void main(String[] args) {
        long start = System.currentTimeMillis();

        solve();
        out.flush();

        long end = System.currentTimeMillis();
        //trace(end-start + "ms");
        sc.close();
    }

    static void trace(Object... o) { System.out.println(deepToString(o));}
}