fn main() {
    let a : u32 = input();
    let b : u32 = input();

    println!("{}", (a|b) - (a&b))
}

fn input<T: std::str::FromStr>() -> T {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().parse().ok().unwrap()
}