n, d = gets.split.map(&:to_i)
[n, d].min.downto(0).each {|a|
  b = (d - a) / 2
  if a + b * 2 == d && n >= a + b
    puts 'A' * a + 'B' * b + 'C' * (n - a - b)
    exit
  end
}