import kotlin.math.min

val MOD = 1_000_000_007

fun main() {
  val (N, X) = readInts()
  val A = readInts()

  val dpL = Array(N){IntArray(N - it + 1)}
  val dpR = Array(N){IntArray(it + 2)}
  val mxR = run {
    val res = IntArray(N)
    var sum = 0L
    var r = N - 1
    for (l in N - 1 downTo 0) {
      sum += A[l]
      while (r > l && sum > X) {
        sum -= A[r]
        r--
      }
      res[l] = r - l + 1
    }
    res
  }
  debug(mxR)
  val mxL = run {
    val res = IntArray(N)
    var sum = 0L
    var l = 0
    for (r in 0 until N) {
      sum += A[r]
      while (l < r && sum > X) {
        sum -= A[l]
        l++
      }
      res[r] = r - l + 1
    }
    res
  }
  debug(mxL)

  for (d in 1 until N) {
    for (l in 0 until N - d) {
      val r = l + d
      val llen = min(d, mxL[r])
      val lwin = dpL[l][d] - dpL[l][d-llen] < llen
      val rlen = min(d, mxR[l])
      val rwin = dpR[r][d] - dpR[r][d-rlen] < rlen
      val win = if (lwin or rwin) 1 else 0
//      debug{"$l $r $win"}
      dpL[l][d+1] = dpL[l][d] + win
      dpR[r][d+1] = dpR[r][d] + win
    }
  }

  debugDim(dpL)
  debugDim(dpR)

  val awin = dpL[0][N] - dpL[0][N - 1] == 1
  if (awin) println("A")
  else println("B")
}












































private val isDebug = try {
  // なんか本番でエラーでる
  System.getenv("MY_DEBUG") != null
} catch (t: Throwable) {
  false
}

private fun readLn() = readLine()!!
private fun readStrings() = readLn().split(" ")
private fun readInts() = readStrings().map { it.toInt() }.toIntArray()
private fun readLongs() = readStrings().map { it.toLong() }.toLongArray()
private inline fun debug(msg: () -> String) {
  if (isDebug) System.err.println(msg())
}
private fun debug(a: LongArray) {
  debug{a.joinToString(" ")}
}
private fun debug(a: IntArray) {
  debug{a.joinToString(" ")}
}
private fun debug(a: BooleanArray) {
  debug{a.map{if(it) 1 else 0}.joinToString("")}
}
private fun debugDim(A: Array<IntArray>) {
  if (isDebug) {
    for (a in A) {
      debug(a)
    }
  }
}