Black and White Stripe

Description:

Input:

The first line contains an integer $$$t$$$ ($$$1 \le t \le 10^4$$$) — the number of test cases.

Next, descriptions of $$$t$$$ test cases follow.

The first line of the input contains two integers $$$n$$$ and $$$k$$$ ($$$1 \le k \le n \le 2\cdot10^5$$$). The second line consists of the letters 'W' (white) and 'B' (black). The line length is $$$n$$$.

It is guaranteed that the sum of values $$$n$$$ does not exceed $$$2\cdot10^5$$$.

Output:

For each of $$$t$$$ test cases print an integer — the minimum number of cells that need to be repainted from white to black in order to have a segment of $$$k$$$ consecutive black cells.

Sample Input:

4
5 3
BBWBW
5 5
BBWBW
5 1
BBWBW
1 1
W

Sample Output:

1
2
0
1

Note:

In the first test case, $$$s$$$="BBWBW" and $$$k=3$$$. It is enough to recolor $$$s_3$$$ and get $$$s$$$="BBBBW". This string contains a segment of length $$$k=3$$$ consisting of the letters 'B'.

In the second test case of the example $$$s$$$="BBWBW" and $$$k=5$$$. It is enough to recolor $$$s_3$$$ and $$$s_5$$$ and get $$$s$$$="BBBBB". This string contains a segment of length $$$k=5$$$ consisting of the letters 'B'.

In the third test case of the example $$$s$$$="BBWBW" and $$$k=1$$$. The string $$$s$$$ already contains a segment of length $$$k=1$$$ consisting of the letters 'B'.