use std::io::Read;

fn main() {
	let mut s = String::new();
	std::io::stdin().read_to_string(&mut s).ok();
	let s: Vec<_> = s.split_whitespace().collect();
	let a = u32::from_str_radix(s[0], 2).unwrap();
	let b = u32::from_str_radix(s[1], 2).unwrap();
	println!("{}", a ^ b)
}