CF——399div2.B.Red and Blue Balls

最新推荐文章于 2024-08-17 22:01:45 发布

原创

最新推荐文章于 2024-08-17 22:01:45 发布 · 458 阅读

0 ·

CC 4.0 BY-SA版权

文章标签：

#数论

B. Red and Blue Balls

time limit per test0.5 seconds
memory limit per test256 megabytes
inputstandard input
outputstandard output
User ainta has a stack of n red and blue balls. He can apply a certain operation which changes the colors of the balls inside the stack.

While the top ball inside the stack is red, pop the ball from the top of the stack.
Then replace the blue ball on the top with a red ball.
And finally push some blue balls to the stack until the stack has total of n balls inside.

If there are no blue balls inside the stack, ainta can’t apply this operation. Given the initial state of the stack, ainta wants to know the maximum number of operations he can repeatedly apply.

Input
The first line contains an integer n (1 ≤ n ≤ 50) — the number of balls inside the stack.

The second line contains a string s (|s| = n) describing the initial state of the stack. The i-th charac