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 {
  var n = scala.io.StdIn.readInt()
  var s = scala.io.StdIn.readLine()

  val firstIndexSharp = s.indexOf("#")
  if(firstIndexSharp < 0) {
    print(0)
  } else {
    val countTarget = s.substring(firstIndexSharp, n)
    val whiteCount = countTarget.count(_ == '.')

    val lastIndexComma = countTarget.lastIndexOf(".")
    val countTarget2 = countTarget.substring(lastIndexComma + 1)
    var blackCount = countTarget2.count(_ == '#')

    if (whiteCount > blackCount) {
      print(blackCount)
    } else {
      print(whiteCount)
    }
  }
}