CF550A.Two Substrings

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).

给你一个字符串 $s$。你的任务是判断给定的字符串 $s$ 是否包含两个不重叠的子串 "AB" 和 "BA"（这两个子串的出现顺序可以任意）。

The only line of input contains a string s of length between 1 and 105 consisting of uppercase Latin letters.

输入仅有一行，包含一个字符串 $s$，其长度在 $1$ 到 $10^5$ 之间，且仅由大写拉丁字母组成。

Print "YES" (without the quotes), if string s contains two non-overlapping substrings "AB" and "BA", and "NO" otherwise.

如果字符串 $s$ 中包含两个不重叠的子串 "AB" 和 "BA"，则输出 "YES"（不带引号）；否则输出 "NO"。

In the first sample test, despite the fact that there are substrings "AB" and "BA", their occurrences overlap, so the answer is "NO".

In the second sample test there are the following occurrences of the substrings: BACFAB.

In the third sample test there is no substring "AB" nor substring "BA".

在第一个样例测试中，尽管存在子串 “AB” 和 “BA”，但它们的出现位置重叠，因此答案为 “NO”。

在第二个样例测试中，子串的出现情况如下：BACFAB。

在第三个样例测试中，既不存在子串 “AB”，也不存在子串 “BA”。