fn main() {
	let mut s = String::new();
	std::io::stdin().read_line(&mut s).ok();
	let mut s = s.trim().split_whitespace();
	let f: u64  = s.next().unwrap().parse().unwrap();
	let ff: u64 = s.next().unwrap().parse().unwrap();
	let n: u64 = s.next().unwrap().parse().unwrap();
	
	let ans = match n % 3 {
		0 => f,
		1 => ff,
		2 => f ^ ff,
		_ => unreachable!(),
	};
	println!("{}", ans);
}