import java.io.PrintWriter
import java.util.*
import kotlin.math.*

fun PrintWriter.solve() {
    val n = nextInt()
    val k = nextInt()
    val a = Array(n) { nextLong() }
    val b = Array(n) { nextLong() }
    val lst = mutableListOf<Pair<Long, Int>>()
    for (i in 0 until n) {
        lst.add(a[i] - b[i] to i)
    }
    lst.sortByDescending { it.first }
    val choice = CharArray(n) { 'B' }
    for (i in 0 until k) {
        val ind = lst[i].second
        choice[ind] = 'A'
    }
    println(choice.joinToString(""))
}

fun main() {
    val writer = PrintWriter(System.out, false)
    writer.solve()
    writer.flush()
}

// region Scanner
private var st = StringTokenizer("")
private val br = System.`in`.bufferedReader()

fun next(): String {
    while (!st.hasMoreTokens()) st = StringTokenizer(br.readLine())
    return st.nextToken()
}

fun nextInt() = next().toInt()
fun nextLong() = next().toLong()
fun nextLine() = br.readLine()
fun nextDouble() = next().toDouble()
// endregion