fn main() {
    let mut ffn = String::new();
    std::io::stdin().read_line(&mut ffn).ok();
    let ffn: Vec<usize> = ffn.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
    let n = ffn[2];
    let mut ff: Vec<usize> = vec![0; 3];
    ff[1] = ffn[0];
    ff[2] = ffn[1];
    ff[0] = ff[1] ^ ff[2];
    println!("{}", ff[(n+1) % 3]);
}