output_description: Print the maximum possible number of happy people after at most K operations.
  
  * * *
input_description: Input is given from Standard Input in the following format:
  
      
      
      N K
      S
attempt: N, K = map(int, input().split())
  
  S = input()
  
  if N == 1:
      print(0)
      exit()
  # 左端をLにする場合
  now = ""
  num_substr = 0
  ex = ""
  stack = []
  for i in range(N):
      if (ex == "L" or ex == "") and S[i] == "R":
          start = i
      if ex == "R" and S[i] == "L":
          end = i - 1
          stack.append((start, end))
          num_substr += 1
      ex = S[i]
  # 左からひっくり返す
  if num_substr == 0:
      print(N - 1)
      exit()
  tmp = min(K, num_substr, N)
  num = stack[tmp - 1][1]
  ss = "L" * (num + 1) + S[num + 1 :]
  ll = num
  
  for i in range(num + 1, N):
      if i == 0:
          if ss[i + 1] == "R" and ss[i] == "R":
              ll += 1
      elif i == N - 1:
          if ss[i - 1] == "L" and ss[i] == "L":
              ll += 1
      else:
          if (ss[i - 1] == "L" and ss[i] == "L") or (ss[i + 1] == "R" and ss[i] == "R"):
              ll += 1
  
  
  # 右からひっくり返す
  if num_substr == 0:
      print(N - 1)
      exit()
  tmp = min(K, num_substr, N)
  num = stack[len(stack) - tmp][0]
  ss = S[: (N - 1 - num)] + "L" * (N - 1 - num)
  
  lr = N - 1 - num
  
  for i in range(num):
      if i == 0:
          if ss[i + 1] == "R" and ss[i] == "R":
              lr += 1
      elif i == N - 1:
          if ss[i - 1] == "L" and ss[i] == "L":
              lr += 1
      else:
          if (ss[i - 1] == "L" and ss[i] == "L") or (ss[i + 1] == "R" and ss[i] == "R"):
              lr += 1
  
  
  ######################################################################
  # 左端をRにする場合
  now = ""
  num_substr = 0
  ex = ""
  stack = []
  for i in range(N):
      if (ex == "R" or ex == "") and S[i] == "L":
          start = i
      if ex == "L" and S[i] == "R":
          end = i - 1
          stack.append((start, end))
          num_substr += 1
      ex = S[i]
  # 左からひっくり返す
  if num_substr == 0:
      print(N - 1)
      exit()
  tmp = min(K, num_substr, N)
  num = stack[tmp - 1][1]
  ss = "R" * (num + 1) + S[num + 1 :]
  rl = num
  # print(ll, tmp)
  for i in range(num + 1, N):
      if i == 0:
          if ss[i + 1] == "R" and ss[i] == "R":
              rl += 1
      elif i == N - 1:
          if ss[i - 1] == "L" and ss[i] == "L":
              rl += 1
      else:
          if (ss[i - 1] == "L" and ss[i] == "L") or (ss[i + 1] == "R" and ss[i] == "R"):
              rl += 1
  
  
  # 右からひっくり返す
  if num_substr == 0:
      print(N - 1)
      exit()
  tmp = min(K, num_substr, N)
  num = stack[len(stack) - tmp][0]
  ss = S[: (N - 1 - num)] + "R" * (N - 1 - num)
  
  rr = N - 1 - num
  # print(ll, tmp)
  for i in range(num):
      if i == 0:
          if ss[i + 1] == "R" and ss[i] == "R":
              rr += 1
      elif i == N - 1:
          if ss[i - 1] == "L" and ss[i] == "L":
              rr += 1
      else:
          if (ss[i - 1] == "L" and ss[i] == "L") or (ss[i + 1] == "R" and ss[i] == "R"):
              rr += 1
  
  
  print(max([ll, lr, rl, rr]))
  
problem_description: 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?
samples: [{"input": "6 1\n    LRLRRL", "output": "3\n    \n\nIf we choose (l, r) = (2, 5), we have `LLLRLL`, where the 2-nd, 3-rd, and 6-th\npersons from the west are happy.\n\n* * *"}, {"input": "13 3\n    LRRLRLRRLRLLR", "output": "9\n    \n\n* * *"}, {"input": "10 1\n    LLLLLRRRRR", "output": "9\n    \n\n* * *"}, {"input": "9 2\n    RRRLRLRLL", "output": "7"}]