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 checkSubstrings(s):
    found_AB = False
    found_BA = False

    for i in range(len(s) - 1):
        if not found_AB and s[i] == 'A' and s[i+1] == 'B':
            found_AB = True
        if not found_BA and s[i] == 'B' and s[i+1] == 'A':
            found_BA = True

        if found_AB and found_BA:
            print("YES")
            return

    print("NO")

a=input()
checkSubstrings(a)
