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 Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.util.Scanner;


public class Main{

	public static void main(String args[]){

		Scanner sc = new Scanner(System.in);

		int n =sc.nextInt();
		String s=sc.next();

		char c[]=new char[n];
		int blackcount=0;
		int blacknum=0;
		int min=n;

		for(int i=0;i<n;++i){
			if(s.charAt(i)=='#')++blacknum;

		}
		for(int i=0;i<n;++i){
			if(s.charAt(i)=='#'){
				++blackcount;
				min=Math.min(min, blackcount-1+(n-1-i)-blacknum+blackcount);
			}
			else min=Math.min(min, blackcount+(n-1-i)-blacknum+blackcount);
		}

		System.out.println(min);


	}
}