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?

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.

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.

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

见题面 Input 部分

见题面 Output 部分