package main

import (
    "fmt"
    "os"
    "bufio"
    "bytes"
    "strconv"
)

const NEW_LINE byte = 10
const SPACE string = " "

type long int64
type float float32
type double float64

type Scanner struct {
    reader *bufio.Reader
    buffer [][]byte
    pointer int
}

func NewScanner() *Scanner {
    scanner := &Scanner{};
    scanner.InitReader()
    return scanner
}

func (self *Scanner) InitReader () {
    self.reader = bufio.NewReaderSize(os.Stdin,4096);
    self.buffer = make([][]byte,0)
    self.pointer = 0
}

func (self *Scanner) Next () string {
    if self.pointer < len(self.buffer) {
        ret := self.buffer[self.pointer]
        self.pointer++
        return string(ret)
    }

    bs,_,_ := self.reader.ReadLine()
    self.buffer = bytes.Split(bs,[]byte(SPACE))
    self.pointer = 0
    return self.Next()
}

func (self *Scanner) NextLine () string {
    b,_,_ := self.reader.ReadLine()
    return string(bytes.TrimSpace(b))
} 

func (self *Scanner) NextInt () int {
    s := self.Next()
    i,_ := strconv.ParseInt(s,10,32)
    return int(i)
}

func (self *Scanner) NextLong () long {
    s := self.Next()
    l,_ := strconv.ParseInt(s,10,64)
    return long(l)
}

func (self *Scanner) NextFloat () float {
    s := self.Next()
    f,_ := strconv.ParseFloat(s,32)
    return float(f)
}

func (self *Scanner) NextDouble () double {
    s := self.Next()
    d,_ := strconv.ParseFloat(s,64)
    return double(d)
}


func main () {
    cin := NewScanner()

	var A long = cin.NextLong();
	var C long = cin.NextLong();
	var B long = A^C;

	fmt.Println(B);
}