fn read_vec<T: std::str::FromStr>() -> Vec<T> {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim()
        .split_whitespace()
        .map(|e| e.parse().ok().unwrap())
        .collect()
}

fn main() {
  let input: Vec<usize> = read_vec();
  println!("{}", no643(input[0], input[1], input[2]));
}

fn no643(f0:usize, f1:usize, n:usize) -> usize {
  let f2 = f1 ^ f0;
  if n % 3 == 0 {
    f0
  } else if n % 3 == 1 {
    f1
  } else {
    f2
  }
}