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 checker():
    s = input()
    first = False
    second  = False
    firstIdx = None
    secondIdx = None

    for i in range(1, len(s)):
        if s[i] == 'A' and s[i-1] == 'B' and i-1 != firstIdx:
            second = True
            secondIdx = i
        
        elif s[i] == 'B' and s[i-1] == 'A' and i-1 != secondIdx:
            first = True
            firstIdx = i
    
    if (first and second):
        print('YES')
    else:
        print('NO')


checker()