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.
import sys
def AB(a, i):
    k1 = False
    while i < len(a):
        if a[i:i+2] == ['A', 'B']:
            k1 = True
            a[i] = '/'
            a[i+1] = '/'
            break
        i += 1
    i = 0
    return k1

def BA(a, i):
    k = False
    while i < len(a):
        if a[i:i+2] == ['B', 'A']:
            k = True
            a[i] = '/'
            a[i+1] = '/'
            break
        i += 1
    i = 0
    return k

b = input()
a = list(b)
c = list(b)
f = 0
f1 = 0
i = 0
f1 = AB(a, i)
f = BA(a, i)
if f1 == f == True:
    print('YES')
    sys.exit()
else:
    a = c
    f = BA(a, i)
    f1 = AB(a, i)
    if f1 == f == True:
        print('YES')
    else:
        print('NO')
