You are given string *s*. Your task is to determine if the given string *s* contains two non-overlapping substrings "AB" and "BA" (the substrings can go in any order).
The only line of input contains a string *s* of length between 1 and 10<sup class="upper-index">5</sup> consisting of uppercase Latin letters.
def f(s):
    if 'AB' in s:
        k = s.index('AB')
        k += 2
        s = s[k:]
        if 'BA' in s:
            return True
    return False


def g(s):
    if 'BA' in s:
        k = s.index('BA')
        k += 2
        s = s[k:]
        if 'AB' in s:
            return True
    return False


s = input()
if f(s) or g(s):
    print('YES')
else:
    print('NO')