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 in = scala.io.Source.stdin.getLines.toSeq
  val S = in.tail.head.toArray
  
  var i = 0
  var wc = 0
  var bc = 0
  var W = S.map(_ => 0)
  var B = S.map(_ => 0)
  while(i<S.size) {
    if(S(i)=='#') bc += 1 else wc += 1
    W(i) = wc
    B(i) = bc
    i += 1
  }
  //println(B.toSeq)
  //println(W.toSeq)
  
  var j = 0
  var ret = Int.MaxValue
  while(j < S.size - 1) {
    val lb = B(j) - 0//B(0)
    val rb = B(S.size-1) - B(j+1)
    val lw = W(j) - 0//W(0)
    val rw = W(S.size-1) - W(j+1)
    //println((lb, lw), (rb, rw))
    ////val tmp = Math.min(lb, lw) + Math.min(rb, rw)
    ////val tmp = Math.min(lb + rw, rb + lw)    
    val tmp = lb + rw    
    //println(ret, tmp)
    ret = Math.min(ret, tmp)
    j += 1
  }
  println(ret)
}