Problem:
Score : 400 points

Problem Statement

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?

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.

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.

Sample Input 1

6 1
LRLRRL

Sample Output 1

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 Input 2

13 3
LRRLRLRRLRLLR

Sample Output 2

9

Sample Input 3

10 1
LLLLLRRRRR

Sample Output 3

9

Sample Input 4

9 2
RRRLRLRLL

Sample Output 4

7

Solution in Kotlin (1.0.0) (judge verdict: Accepted)

fun main(args: Array<String>) {

    val (n, k) = readLine()!!.split(" ").map(String::toInt)
    val s = readLine()!!

    println(abc140d(n, k, s))
}


fun abc140d(n: Int, k: Int, s: String): Any? {

    val initScore = countHappy(s)

    return Math.min(initScore + 2 * k, s.length - 1)
}

fun countHappy(s: String): Int {
    var count = 0
    for (i in s.indices) {

        // 右端と左端は特別
        if (i == 0) {

            if (s[i] == 'L') {
                continue
            }

            if (s.length < 2) {
                continue
            }

            if (s[i + 1] == 'R') {
                count++
            }
            continue
        }
        if (i == s.length - 1) {
            if (s[i] == 'R') {
                continue
            }

            if (s[i - 1] == 'L') {
                count++
            }
            continue
        }

        if (s[i] == 'L') {
            if (s[i] == s[i - 1]) {
                count++
            }
        } else {
            if (s[i] == s[i + 1]) {
                count++
            }
        }
    }

    return count
}