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 ifexist(string, f, s):
    for i in range(1,len(string)):
        if string[i-1] + string[i] == f:
            for j in range(i+2, len(string)):
                if string[j-1] + string[j] == s:
                    return True
            break
    return False

if __name__ == '__main__':
    s=input()
    if ifexist(s, 'AB', 'BA') or ifexist(s, 'BA', 'AB'):
        print('YES')
    else:
        print('NO')