Contest Duration: - (local time) (100 minutes) Back to Home
B - Quizzes /

Time Limit: 2 sec / Memory Limit: 1024 MB

### 問題文

ただし、持っている点数が 0 点のときに不正解となった場合は点数は減りません。

S の左から i 番目の文字が o のとき、 i 問目が正解だったことを、 x のとき、 i 問目が不正解だったことを表します。

### 制約

• 1 \le N \le 2 \times 10^5
• 0 \le X \le 2 \times 10^5
• Sox からなる長さ N の文字列

### 入力

N X
S


### 入力例 1

3 0
xox


### 出力例 1

0


はじめ、高橋くんの点数は 0 です。
1 問目は不正解ですが、点数が 0 なので減りません。
2 問目は正解なので、点数が増えて 1 になります。
3 問目は不正解なので、点数が減って 0 になります。 高橋くんの最終的な点数は 0 なので、0 を出力します。

### 入力例 2

20 199999
oooooooooxoooooooooo


### 出力例 2

200017


### 入力例 3

20 10
xxxxxxxxxxxxxxxxxxxx


### 出力例 3

0


Score : 200 points

### 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