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: Wrong Answer)

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();

		CountNumberOfConversions countNumberOfConversions = new CountNumberOfConversions();

		System.out.println(countNumberOfConversions.getReplaceCount(N,S));
	}
}

class CountNumberOfConversions {
	public int getReplaceCount(int N,String S) {
		int result = 0;
		String key = S.substring(N-1, N);
		String black =getBlack(key);
		String white =getWhite(key);
		boolean conversionFlag = false;

		String[] strArray = S.split("");
		for(String s : strArray) {
			if(!conversionFlag) {
				if(s.endsWith(black)) {
					conversionFlag = true;
				}

			}else if(conversionFlag) {
				if(s.equals(white)) {
					result++;
				}
			}
		}
		return result;
	}

	public String getBlack(String key) {
		return checkBlackOrWhite(key,"black");
	}

	public String getWhite(String key) {
		return checkBlackOrWhite(key,"white");
	}

	public String checkBlackOrWhite(String key,String input) {
		String result = ".";
		if(key.equals("#")) {
			if(input.equals("black")) {
				result="#";
			}
		}else {
			if(!input.equals("black")) {
				result="#";
			}
		}
		return result;
	}

}