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();
        String[] str = s.split("");

        int allBlackCount = 0;
        for (int i = 0; i < str.length; i++) {
            if (".".equals(str[i])) {
                allBlackCount++;
            }
        }
        int allWhiteCount = 0;
        for (int i = 0; i < str.length - 1; i++) {
            if ("#".equals(str[i])) {
                allWhiteCount++;
            }
        }
        int whiteStartCount = 0;
        boolean whiteZone1 = true;
        boolean blackZone1 = false;
        for (int i = 0; i < str.length; i++) {
            if ("#".equals(str[0])) {
                whiteStartCount = Integer.MAX_VALUE;
                break;
            }
            if (whiteZone1 && !blackZone1 && ".".equals(str[i])) {
                continue;
            }
            if (whiteZone1 && !blackZone1 && "#".equals(str[i])) {
                whiteZone1 = false;
                blackZone1 = true;
                continue;
            }
            if (!whiteZone1 && blackZone1 && "#".equals(str[i])) {
                continue;
            }
            if (!whiteZone1 && blackZone1 && ".".equals(str[i])) {
                whiteZone1 = true;
                whiteStartCount++;
                continue;
            }
            if (whiteZone1 && blackZone1 && "#".equals(str[i])) {
                continue;
            }
            whiteStartCount++;
        }

        int blackStartCount = 0;
        boolean whiteZone2 = false;
        boolean blackZone2 = false;
        for (int i = 0; i < str.length; i++) {
            if (".".equals(str[0])) {
                blackStartCount = Integer.MAX_VALUE;
                break;
            }
            if (!whiteZone2 && !blackZone2 && "#".equals(str[i])) {
                blackStartCount++;
                continue;
            }
            if (!whiteZone2 && !blackZone2 && ".".equals(str[i])) {
                whiteZone2 = true;
                continue;
            }
            if (whiteZone2 && !blackZone2 && ".".equals(str[i])) {
                continue;
            }
            if (whiteZone2 && !blackZone2 && "#".equals(str[i])) {
                whiteZone2 = false;
                blackZone2 = true;
                continue;
            }
            if (!whiteZone2 && blackZone2 && "#".equals(str[i])) {
                continue;
            }
            if (!whiteZone2 && blackZone2 && ".".equals(str[i])) {
                blackStartCount++;
                whiteZone2 = true;
                blackZone2 = true;
                continue;
            }
            if (whiteZone2 && blackZone2 && "#".equals(str[i])) {
                continue;
            }
            blackStartCount++;
        }
        System.out.println(Math.min(whiteStartCount,
                Math.min(blackStartCount, Math.min(allWhiteCount, allBlackCount))));
    }

}