Face Produces Unhappiness

AtCoder

IDabc140_d

Time2000ms

Memory256MB

Difficulty—

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: $N$ $K$ $S$ [samples]

Samples

Input #1

6 1
LRLRRL

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.

Input #2

13 3
LRRLRLRRLRLLR

Output #2

Input #3

10 1
LLLLLRRRRR

Output #3

Input #4

9 2
RRRLRLRLL

Output #4

API Response (JSON)

{
  "problem": {
    "name": "Face Produces Unhappiness",
    "description": {
      "content": "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 $i$\\-t",
      "description_type": "Markdown"
    },
    "platform": "AtCoder",
    "limit": {
      "time_limit": 2000,
      "memory_limit": 262144
    },
    "difficulty": "None",
    "is_remote": true,
    "is_sync": true,
    "sync_url": null,
    "sign": "abc140_d"
  },
  "statements": [
    {
      "statement_type": "Markdown",
      "content": "There are $N$ people standing in a queue from west to east.\nGiven 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 $i$\\-t...",
      "is_translate": false,
      "language": "English"
    }
  ]
}

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