n = int(input())

from functools import *

@cache
def f(n):
  if n==1:
    return 0
  T = set()
  if n>=2: T.add(f(n//2)^f((n+1)//2))
  if n>=3: T.add(f(n//3)^f((n+1)//3)^f((n+2)//3))
  cnt = 0
  while cnt in T:
    cnt += 1
  return cnt

if f(n):
  print('A')
else:
  print('B')