import scala.annotation.tailrec
import scala.io.StdIn.*




@main def main =
  val Array(n, k) = readLine().split(' ').map(_.toInt)
  val a = readLine().split(' ').map(_.toLong)
  val b = readLine().split(' ').map(_.toLong)
  val result = Array.fill(n){'B'}
  for i <- (0 until n).sortWith{(i, j) => (a(j) - b(j)) < (a(i) - b(i))}.take(k) do
    result(i) = 'A'
  println(result.mkString)