101841: [AtCoder]ABC184 B - Quizzes

Problem Statement

Takahashi will answer $N$ quiz questions.
Initially, he has $X$ points. Each time he answers a question, he gains $1$ point if his answer is correct and loses $1$ point if it is incorrect.
However, there is an exception: when he has $0$ points, he loses nothing for answering a question incorrectly.

You will be given a string $S$ representing whether Takahashi's answers are correct.
If the $i$-th character of $S$ from the left is o, it means his answer for the $i$-th question is correct; if that character is x, it means his answer for the $i$-th question is incorrect.
How many points will he have in the end?

Constraints

• $1 \le N \le 2 \times 10^5$
• $0 \le X \le 2 \times 10^5$
• $S$ is a string of length $N$ consisting of o and x.

Input

Input is given from Standard Input in the following format:

$N$ $X$
$S$

Output

Print the number of points Takahashi will have in the end.

Sample Input 1

3 0
xox

Sample Output 1

0

Initially, he has $0$ points.
He answers the first question incorrectly but loses nothing because he has no point.
Then, he answers the second question correctly, gains $1$ point, and now has $1$ point.
Finally, he answers the third question incorrectly, loses $1$ point, and now has $0$ points.
Thus, he has $0$ points in the end. We should print $0$.

Sample Input 2

20 199999
oooooooooxoooooooooo

Sample Output 2

200017

Sample Input 3

20 10
xxxxxxxxxxxxxxxxxxxx

Sample Output 3

0