Problem:
Score : 300 points

Problem Statement

There are N stones arranged in a row. Every stone is painted white or black.
A string S represents the color of the stones. The i-th stone from the left is white if the i-th character of S is ., and the stone is black if the character is #.

Takahashi wants to change the colors of some stones to black or white so that there will be no white stone immediately to the right of a black stone.
Find the minimum number of stones that needs to be recolored.

Constraints

1 \leq N \leq 2\times 10^5

S is a string of length N consisting of . and #.

Input

Input is given from Standard Input in the following format:

N
S

Output

Print the minimum number of stones that needs to be recolored.

Sample Input 1

3
#.#

Sample Output 1

1

It is enough to change the color of the first stone to white.

Sample Input 2

5
#.##.

Sample Output 2

2

Sample Input 3

9
.........

Sample Output 3

0

Solution in Scala (2.11.7) (judge verdict: Wrong Answer)

object Main extends App {
  val inputs: Seq[String] = scala.io.Source.stdin.getLines().toList
  val N = inputs(0).toInt
  val S = inputs(1)

  println(solve(N,S))

  def solve(length: Int, rocks: String): Int  = {
    var varRocks = rocks
    var resultWhite = 0
    var resultBrack = 0
    // 白にする
    while (varRocks.contains("#.")) {
      resultWhite = resultWhite + varRocks.split("#.").length -1
      varRocks = varRocks.replaceAll("#.", "..")
    }
    // 黒にする
    varRocks = rocks
    while (varRocks.contains("#.")) {
      resultBrack = resultBrack + varRocks.split("#.").length -1
      varRocks = varRocks.replaceAll("#.", "..")
    }

    val result = if (resultBrack < resultWhite) resultBrack else resultWhite
    if (result <= 0) {
      0
    } else {
      result
    }
  }
}