N, K = gets.split.map(&:to_i)
A = gets.split.map(&:to_i)
B = gets.split.map(&:to_i)
G = A.zip(B).map.with_index { |(a, b), i| [a, b, i] }
G.sort_by! { |a, b, _| b - a }
ans = Array.new(N, 'B')

K.times do |k|
  a, b, i = G[k]
  ans[i] = 'A'
end

puts ans.join