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 math
def error(*n):
    print("[Err]",end=" ")
    for i in n:
        print(i,end=" ")
    print()

##n,m = [int(i) for i in input().split()]
##if type(n) == list:
##    n = n[0]

s = input()
a=s.find("AB")
b=s.rfind("BA")
if abs(a-b)<=1:
    print("NO")
else:
    print("YES")

  	 					 	  	 	 		  			 	 	  	