=begin
0 0 > 0
0 1 > 1
1 0 > 1
1 1 > 0
---
0 0 > 0
0 1 > 1
1 1 > 0
1 0 > 1
---
0 0 > 0
0 1 > 1
1 0 > 1
1 1 > 0
=end
a, c = gets.chomp.split.map &:to_i
b = a ^ c
p b