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: Accepted)

object Main{
	def main(args:Array[String]){
		val s = new java.util.Scanner(System.in)
		val n = s.nextInt
		val t = s.next
		val b,w = Array.fill(n+2)(0)

		for(i <- 0 to n - 1)
			b(i+1) = b(i) + (if(t.charAt(i) == '#') 1 else 0)
		for(i <- n-1 to 0 by -1)
			w(i+1) = w(i+2) + (if(t.charAt(i) == '.') 1 else 0)


//		println(b.mkString(" "))
//		println(w.mkString(" "))

		println((0 to n).map(i=>b(i)+w(i+1)).min)
	}
}