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)

import scala.io.StdIn

object Main extends App {
  val n  = StdIn.readLine().toInt
  val s  = StdIn.readLine()

  def solve2(s: String): Int = {
    var p  = '.'
    var ac = 0
    var index = 0
    var min = Int.MaxValue
    val last = s.length() + 1

    if (s.contains("#.")) {
      s.foreach {v =>
        if (v == '#') {
          ac += 1
        } else { // v = '.'
          if (p == '#') {
            var l = s.slice(index + 1, last).count(_ == '.')
            var r = ac
            if (min > l + r) min = l + r
          }
        }
        p = v;
        index += 1
      }
      min
    } else {
      0
    }
  }

  
  println(solve2(s))


}