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 C (GCC 5.4.1) (judge verdict: Accepted)

#include <stdio.h>
#include <stdlib.h>

typedef struct stringBlock
{
    int startIndex;
    int endIndex;
    int length;
    char moji;
} block;

void initialization(block *judgeBlock, int inputN)
{
    for (int count = 0; count < inputN; count++)
    {
        block tmp;
        tmp.length = 0;
        judgeBlock[count] = tmp;
    }
}

int main(void)
{
    int inputN, inputK, startIndex = 0, endIndex, answer = 0, emptyNum = 0, changeCount = 0;
    char *inputS;
    block *judgeBlock;
    
    scanf("%d%d", &inputN, &inputK);
    inputS = (char *)malloc(sizeof(char) * inputN + 1);
    judgeBlock = (block *)malloc(sizeof(block) * inputN);
    initialization(judgeBlock, inputN);
    scanf("%s", inputS);

    for (int count = 0; count < inputN; count++)
    {
        if (inputS[count] != inputS[count + 1])
        {
            endIndex = count;
            judgeBlock[emptyNum].startIndex = startIndex;
            judgeBlock[emptyNum].endIndex = endIndex;
            judgeBlock[emptyNum].length = endIndex - startIndex + 1;
            judgeBlock[emptyNum].moji = inputS[count];
            emptyNum++;
            startIndex = count + 1;
        }
    }
    for (int count = 0; count < emptyNum; count++)
    {
        if (count % 2 != 0)
        {
            if (judgeBlock[count].moji == 'R')
            {
                judgeBlock[count].moji = 'L';
            }
            else
            {
                judgeBlock[count].moji = 'R';
            }
            changeCount++;
        }
        if (changeCount == inputK)
        {
            break;
        }
    }
    for (int count = 0; count < emptyNum; count++)
    {
        for (int innercount = judgeBlock[count].startIndex; innercount <= judgeBlock[count].endIndex; innercount++)
        {
            inputS[innercount] = judgeBlock[count].moji;
        }
    }
    for (int count = 0; count < inputN; count++)
    {
        if (inputS[count] == inputS[count + 1])
        {
            answer++;
        }
    }
    printf("%d", answer);

    free(inputS);
    free(judgeBlock);

    return 0;
}