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) {
        // C - Stones

        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt();
        String s = sc.next();
        
        char[] c = s.toCharArray();
        
        int countB = 0;
        int countW = 0;
        boolean isBlack = false;
        boolean isWhite = false;
            
        for (int i = 0, j = n -1; i < n; i++, j--) {
            if (c[i] == '#') {
                isBlack = true;
            } else if (isBlack) {
                ++countB;
            }
            if (c[j] == '.') {
                isWhite = true;
            } else if (isWhite) {
                ++countW;
            }
        }

        System.out.println((countB < countW ?  countB : countW));
    }

}