use std::io;

fn main() {
    let mut input = String::new();
    io::stdin().read_line(&mut input).ok();
    let mut input = input.split_whitespace();
    let f0 = input.next().unwrap().parse::<u64>().unwrap();
    let f1 = input.next().unwrap().parse::<u64>().unwrap();
    let n = input.next().unwrap().parse::<u64>().unwrap();

    let f = [f0, f1, f0 ^ f1];

    println!("{}", f[(n % 3) as usize]);
}