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){
        Scanner sc = new Scanner(System.in);
        
        int n = sc.nextInt();
        String s = sc.next();
        
        int countb = 0;
        int countw = 0;

        for (int i = 0; i < s.length(); i++){
            String cha = s.substring(i, i + 1);

            if (cha.equals("#")) {
                countb++;
            } else {
                countw++;
            } 

        }

        if (countb > countw && s.substring(0, 1).equals(".")) {
            countw--;
            System.out.println(countw);
        } else if (countb > countw) {
            System.out.println(countw);
        } else if (s.substring(n - 1, n).equals("#")) {
            countb--;
            System.out.println(countb);
        } else {
            System.out.println(countb);
        }


     }
}