// No.2323 Nafmo、A+Bをする
package main

import (
	"fmt"
	"strconv"
)

func main() {
	var a, b string
	fmt.Scan(&a, &b)

	lpad := func(s string, pad string, length int) string {
		for i := len(s); i < length; i++ {
			s = pad + s
		}
		return s
	}

	l := max(len(a), len(b))
	aa := lpad(a, "0", l)
	bb := lpad(b, "0", l)

	var s string
	for j := 0; j < l; j++ {
		if aa[j] != bb[j] {
			s = s + "1"
		} else {
			s = s + "0"
		}
	}
	ans, _ := strconv.ParseInt(s, 2, 0)
	fmt.Println(ans)
}