a, b, c = gets.split.map(&:to_i)

case [a, b, c].uniq.size
when 1
  puts a
when 2
  if a == b
    puts c
  elsif a == c
    puts b
  else
    puts a
  end
when 3
  puts ([0, 1, 2, 3] - [a, b, c])[0]
end