Problem10764--ABC140 - D - Face Produces Unhappiness

10764: ABC140 - D - Face Produces Unhappiness

[Creator : ]
Time Limit : 1.000 sec  Memory Limit : 512 MiB

Description

There are $N$ people standing in a queue from west to east.

Given is a string $S$ of length $N$ representing the directions of the people. The $i$-th person from the west is facing west if the $i$-th character of $S$ is `L`, and east if that character of $S$ is `R`.

A person is happy if the person in front of him/her is facing the same direction. If no person is standing in front of a person, however, he/she is not happy.

You can perform the following operation any number of times between $0$ and $K$ (inclusive):

Operation: Choose integers $l$ and $r$ such that $1 \leq l \leq r \leq N$, and rotate by $180$ degrees the part of the queue: the $l$-th, $(l+1)$-th, $...$, $r$-th persons. That is, for each $i = 0, 1, ..., r-l$, the $(l + i)$-th person from the west will stand the $(r - i)$-th from the west after the operation, facing east if he/she is facing west now, and vice versa.

What is the maximum possible number of happy people you can have?

Input

Input is given from Standard Input in the following format:

```
$N$ $K$
$S$
```

Output

Print the maximum possible number of happy people after at most $K$ operations.

Constraints

-   $N$ is an integer satisfying $1 \leq N \leq 10^5$.
-   $K$ is an integer satisfying $1 \leq K \leq 10^5$.
-   $|S| = N$
-   Each character of $S$ is `L` or `R`.

Sample 1 Input

6 1
LRLRRL

Sample 1 Output

3

If we choose $(l, r) = (2, 5)$, we have LLLRLL, where the $2$-nd, $3$-rd, and $6$-th persons from the west are happy.

Sample 2 Input

13 3
LRRLRLRRLRLLR

Sample 2 Output

9

Sample 3 Input

10 1
LLLLLRRRRR

Sample 3 Output

9

9 2
RRRLRLRLL

7

Source/Category