N, D = gets.split.map(&:to_i)

if D == 0
  puts 'C' * N
elsif D == 1
  puts 'A' + 'C' * (N - 1)
else
  x = N
  y = 0

  while x + 2 * y != D
    x -= 1
    y += 1
  end

  puts 'A' * x + 'B' * y
end