from numpy import *
A=int64(open(0).read().split())
N,X=A[:2]
A=A[2:]
l=r=A*0
for n in range(1,N):
  l=l[1:]+A[:-n]
  r=r[:-1]+A[n:]
  i=(l>X)&(r>X)
  l*=~i
  r*=~i
print('A' if l[0] else 'B')