fn main() {
    let mut input = String::new();
    std::io::stdin().read_line(&mut input).ok();

    let input = input
        .split_whitespace()
        .map(|x| x.parse::<u64>().unwrap())
        .collect::<Vec<_>>();
    let (f0, f1, n) = (input[0], input[1], input[2]);

    println!(
        "{}",
        match n % 3 {
            0 => f0,
            1 => f1,
            2 => f0 ^ f1,
            _ => panic!(),
        }
    );
}