# Aが最も多くなるように
def f(n, d)
  if n < d
    m = d-n
    f(n-m, n-m) + "B"*m
  elsif n > d
    m = n-d
    f(n-m, n-m) + "C"*m
  elsif n == d
    "A"*n
  end
end

N, D = gets.split(" ").take(2).map(&:to_i)
puts f(N, D)