use std::io::{stdin, BufRead};

fn main() {
    let mut buf = String::new();
    let mut stdin = stdin().lock();

    let a = {
        stdin.read_line(&mut buf).unwrap();
        i32::from_str_radix(buf.trim_end(), 2).unwrap()
    };

    let b = {
        buf.clear();
        stdin.read_line(&mut buf).unwrap();
        i32::from_str_radix(buf.trim_end(), 2).unwrap()
    };

    println!("{}", a ^ b)
}