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: Time Limit Exceeded)

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {

	public static void main(String[] args) {
		//Scanner sc = new Scanner(System.in);
		BufferedReader bf=new BufferedReader(new InputStreamReader(System.in));

		try {

String num = bf.readLine();
			int number = Integer.parseInt(num);

			//int number = bf.read();


			String str=bf.readLine();




		int sum=0;

		int z=0;


		//
			while(z<number) {

				int count=0;
				int count2=0;



					while(str.charAt(z)=='#') {
						count++;
						z++;
						if(z>=number) break;}

						if(z>=number) break;
					while(str.charAt(z)=='.' && count2<count) {
						count2++;
						sum++;
						z++;
						if(z>=number) break;
					}


					//z--;



	}
			//sc.close();
		System.out.print(sum);}catch (IOException e) {
			// TODO 自動生成された catch ブロック
			e.printStackTrace();
		}

}}