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 {
  def foo(n: Int, s: String): Unit = {
    if (s.count(_ == '#') == 0) {
      println(0)
    }
    else {
      val ns = s.substring(s.indexOf('#'), s.length)
      println(
        math.min(ns.count(_ == '.'),
          ns.count(_ == '#')))
    }
  }
  foo(readInt(), readLine.toString)
}