fn main() {
	let mut s = String::new();
	std::io::stdin().read_line(&mut s).ok();
	let mut f: Vec<u64> = s.split_whitespace().flat_map(str::parse).collect();
	let n = f.pop().unwrap() as usize;
	(2..=n).for_each(|i| f.push(f[i - 1] ^ f[i - 2]));
	println!("{}", f[n])
}