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

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

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