fn read() -> String {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().to_string()
}

fn main() {
    let a = usize::from_str_radix(&read(), 2).unwrap();
    let b = usize::from_str_radix(&read(), 2).unwrap();
    println!("{}", a ^ b);
}