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 PyPy3 (2.4.0) (judge verdict: Runtime Error)

n, k = map(int, input().split())
s = input()

l_array = [0 for x in range(n)]
l_reverse = []
r_array = [0 for x in range(n)]
r_reverse = []

cnt = []
l_cnt = 0
r_cnt = 0
now = s[0]
for index, ss in enumerate(s):
    if ss == "L":
        if now == ss:
            l_cnt += 1
        else:
            cnt.append(r_cnt)
            r_cnt = 0
            l_cnt = 1
            now = "L"
    else:
        if now == ss:
            r_cnt += 1
        else:
            cnt.append(l_cnt)
            l_cnt = 0
            r_cnt = 1
            now = "R"
else:
    cnt.append(max(l_cnt, r_cnt))

len_cnt = len(cnt)
res = []
for i in range(0, len_cnt, 2):
    if i+1>=len_cnt: continue
    res.append(cnt[i]+cnt[i+1])
res = sorted(res, reverse=True)
ans = 0
for j in range(k):
    ans += res[j]
print(ans)