VK Cup 2012 Finals (unofficial online-version)
C
Cowboys
Codeforces
2100
原题
← BD →
翻译中…

A very tense moment: $*n*$ cowboys stand in a circle and each one points his colt at a neighbor. Each cowboy can point the colt to the person who follows or precedes him in clockwise direction. Human life is worthless, just like in any real western.

翻译中…

The picture changes each second! Every second the cowboys analyse the situation and, if a pair of cowboys realize that they aim at each other, they turn around. In a second all such pairs of neighboring cowboys aiming at each other turn around. All actions happen instantaneously and simultaneously in a second.

翻译中…

We'll use character "A" to denote a cowboy who aims at his neighbour in the clockwise direction, and character "B" for a cowboy who aims at his neighbour in the counter clockwise direction. Then a string of letters "A" and "B" will denote the circle of cowboys, the record is made from the first of them in a clockwise direction.

翻译中…

For example, a circle that looks like "ABBBABBBA" after a second transforms into "BABBBABBA" and a circle that looks like "BABBA" transforms into "ABABB".

翻译中…

image This picture illustrates how the circle "BABBA" transforms into "ABABB"

翻译中…

A second passed and now the cowboys' position is described by string $*s*$. Your task is to determine the number of possible states that lead to $*s*$ in a second. Two states are considered distinct if there is a cowboy who aims at his clockwise neighbor in one state and at his counter clockwise neighbor in the other state.

翻译中…

Input

翻译中…

The input data consists of a single string $*s*$. Its length is from 3 to 100 characters, inclusive. Line $*s*$ consists of letters "A" and "B".

翻译中…

Output

翻译中…

Print the sought number of states.

翻译中…

Note

翻译中…

In the first sample the possible initial states are "ABBBABBAB" and "ABBBABBBA".

翻译中…

In the second sample the possible initial states are "AABBB" and "BABBA".

翻译中…

样例

Input #1
BABBBABBA
Output #1
2
InputCopy OutputCopy
Input #2
ABABB
Output #2
2
InputCopy OutputCopy
Input #3
ABABAB
Output #3
4
InputCopy OutputCopy
题目信息
题号
212C
时间限制
2 s
内存限制
256 MB
标签
组合数学
动态规划
数学

题面与样例版权归 Codeforces 及出题人所有;中文翻译由 AI 生成(CI 管线),如有出入请以原文为准。