import kotlin.math.max
import kotlin.math.min

val MOD = 1_000_000_007

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

  if (N == 1) {
    println("B")
    return
  }

  val dpL = Array(N){SegmentTree(N - it, true){a, b -> a and b}}
  val dpR = Array(N){SegmentTree(it + 1, true){a, b -> a and b}}
  for (i in 0 until N) {
    // １個だけ残ってる場合はlose
    dpL[i].update(0, false)
    dpR[i].update(0, false)
  }
  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 (len in 2 until N + 1) {
    for (l in 0 until N - len) {
      val r = l + len - 1
      val win = !dpL[l].query(max(0, len-1-mxL[r]), len-1) or
              !dpR[r].query(max(0, len-1-mxR[l]), len-1)
      dpL[l].update(len - 1, win)
      dpR[r].update(len - 1, win)
    }
  }
  if (dpL[0].query(N-1, N)) println("A")
  else println("B")
}

class SegmentTree(n: Int, val zero: Boolean, val f: (Boolean, Boolean) -> Boolean) {
  private val N =
    if (Integer.highestOneBit(n) == n) n
    else Integer.highestOneBit(n) shl 1

  private val dat = BooleanArray(2 * N){zero}

  fun update(i: Int, a: Boolean) {
    var ix = i + N
    dat[ix] = a
    while(ix > 1) {
      dat[ix shr 1] = f(dat[ix], dat[ix xor 1])
      ix = ix shr 1
    }
  }

  /**
   * [a, b)
   */
  fun query(a: Int, b: Int): Boolean {
    var res: Boolean = zero
    var left = a + N
    var right = b - 1 + N

    while(left <= right) {
      if ((left and 1) == 1) res = f(res, dat[left])
      if ((right and 1) == 0) res = f(res, dat[right])
      left = (left + 1) shr 1 // 右の子供なら右の親に移動
      right = (right - 1) shr 1 // 左の子供なら左の親に移動
    }

    return res
  }
}












































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)
    }
  }
}