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: Time Limit Exceeded)

import scala.util.control.Breaks

object Main extends App {
  var n = scala.io.StdIn.readInt()
  var s = scala.io.StdIn.readLine()
  var count = 0
  val b = new Breaks
  b.breakable{
    while(true) {
      if(s.indexOf("#.") < 0) {
        b.break()
      } else {
        if(s.indexOf("#.#") >= 0) {
          s = s.replaceFirst("#\\.#", "###")
          count = count + 1
        } else if (s.indexOf("#..") >= 0) {
          s = s.replaceFirst("#\\.\\.", "...")
          count = count + 1
        } else {
          s = s.replaceFirst("#\\.", "¥¥")
          count = count + 1
        }
      }

    }

  }
  print(count)
}