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.*;
public class Main {
	public static void main(String[] args){
		long start = System.currentTimeMillis();
		
		char black = '#';
		char white = '.';
		
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		String s = sc.next();
		
		char[] inputChars = s.toCharArray();
		
		int noneedright = 0;
		for(int i = s.length() -1; i >= 0; i--) {
			if(inputChars[i] == black) {
				noneedright++;
			}
			if(inputChars[i] == white) {
				break;
			}
		}
		int noneedleft = 0;
		for(int i = 0; i < s.length(); i++) {
			if(inputChars[i] == white) {
				noneedleft++;
			}
			if(inputChars[i] == black) {
				break;
			}
		}
		
		char[] chars = Arrays.copyOfRange(inputChars, noneedleft, s.length() - noneedright);

		int ans = 0;
		
		int tempBlack = 0;
		int tempWhite = 0;
		for(int i = 0; i < chars.length; i++) {
			
			if(chars[i] == black) {
				tempBlack++;
			} else {
				tempWhite++;
			}
		}
		if(tempBlack > tempWhite) {
			ans = tempWhite;
		} else {
			ans = tempBlack;
		}
		
		String reString = "" + ans;
		System.out.println(reString);
	}
	
}