pub mod scanner {

    pub struct Scanner {
        buf: Vec<String>,
    }

    impl Scanner {
        pub fn new() -> Self {
            Self { buf: vec![] }
        }

        pub fn new_from(source: &str) -> Self {
            let source = String::from(source);
            let buf = Self::split(source);
            Self { buf }
        }

        pub fn next<T: std::str::FromStr>(&mut self) -> T {
            loop {
                if let Some(x) = self.buf.pop() {
                    return x.parse().ok().expect("");
                }
                let mut source = String::new();
                std::io::stdin().read_line(&mut source).expect("");
                self.buf = Self::split(source);
            }
        }

        fn split(source: String) -> Vec<String> {
            source
                .split_whitespace()
                .rev()
                .map(String::from)
                .collect::<Vec<_>>()
        }
    }
}

use crate::scanner::Scanner;

fn main() {
    let mut scanner = Scanner::new();
    let t: usize = 1;
    for _ in 0..t {
        solve(&mut scanner);
    }
}

fn solve(scanner: &mut Scanner) {
    let a2: Vec<char> = scanner.next::<String>().chars().map(|c| c).collect();
    let b2: Vec<char> = scanner.next::<String>().chars().map(|c| c).collect();
    let mut a = 0;
    for &c in a2.iter() {
        a *= 2;
        if c == '1' {
            a += 1;
        }
    }
    let mut b = 0;
    for &c in b2.iter() {
        b *= 2;
        if c == '1' {
            b += 1;
        }
    }
    println!("{}", a ^ b);
}