XYYYX

AtCoder

IDarc157_b

Time2000ms

Memory256MB

Difficulty—

You are given a string $S$ of length $N$ consisting of `X` and `Y`. You will choose $K$ characters at distinct positions in $S$ and change each of them: `X` becomes `Y` and `Y` becomes `X`. Find the maximum possible number of pairs of consecutive `Y`s in the resulting string. ## Constraints * $1 \leq N \leq 2 \times 10^5$ * $0 \leq K \leq N$ * $S$ is a string of length $N$ consisting of `X` and `Y`. ## Input The input is given from Standard Input in the following format: $N$ $K$ $S$ [samples]

Samples

Input #1

5 1
XYXYX

Output #1

2

You will choose one character.

*   If you choose the $1$\-st character, the resulting string is `YYXYX`, with one pair of consecutive `Y`s at positions $1, 2$.
*   If you choose the $2$\-nd character, the resulting string is `XXXYX`, with no pair of consecutive `Y`s.
*   If you choose the $3$\-rd character, the resulting string is `XYYYX`, with two pairs of consecutive `Y`s at positions $2, 3$ and $3, 4$.
*   If you choose the $4$\-th character, the resulting string is `XYXXX`, with no pair of consecutive `Y`s.
*   If you choose the $5$\-th character, the resulting string is `XYXYY`, with one pair of consecutive `Y`s at positions $4, 5$.

Thus, the sought maximum number is $2$.

Input #2

5 4
XYXYX

Output #2

2

It is optimal to choose the $1$\-st, $2$\-nd, $3$\-rd, and $5$\-th characters to get `YXYYY`, or choose the $1$\-st, $3$\-rd, $4$\-th, and $5$\-th characters to get `YYYXY`. Note that you may not choose a character at the same position multiple times.

API Response (JSON)

{
  "problem": {
    "name": "XYYYX",
    "description": {
      "content": "You are given a string $S$ of length $N$ consisting of `X` and `Y`. You will choose $K$ characters at distinct positions in $S$ and change each of them: `X` becomes `Y` and `Y` becomes `X`. Find the m",
      "description_type": "Markdown"
    },
    "platform": "AtCoder",
    "limit": {
      "time_limit": 2000,
      "memory_limit": 262144
    },
    "difficulty": "None",
    "is_remote": true,
    "is_sync": true,
    "sync_url": null,
    "sign": "arc157_b"
  },
  "statements": [
    {
      "statement_type": "Markdown",
      "content": "You are given a string $S$ of length $N$ consisting of `X` and `Y`. You will choose $K$ characters at distinct positions in $S$ and change each of them: `X` becomes `Y` and `Y` becomes `X`. Find the m...",
      "is_translate": false,
      "language": "English"
    }
  ]
}

Full JSON Raw Segments