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) {
        //変数
        int count = 0;
        boolean sw = false;
        int max = Integer.MIN_VALUE;
        int min = Integer.MAX_VALUE;
        int answer = 0;
        List<Integer> list1 = new ArrayList<>();
        List<Integer> list2 = new ArrayList<>();
        int array1[] = new int[5];
        int array2[] = new int[5];
        List<String> slist = new ArrayList<>();
        //入力
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        String S = sc.next();
        //処理
        String siro = ".";//白
        String kuro = "#";//黒
        String ss = "";
        int point = 0;
        int bcount = 0;
        for (int i = 0; i < N; i++) {
            ss = S.substring(i, i + 1);
            if (ss.equals("#")) {
                point = i;
                break;
            }
        }

        for (int i = point; i < N; i++) {
            ss = S.substring(i, i + 1);
            if (ss.equals(siro)) {
                count++;
            } else {
                bcount++;
            }
        }


        if (count > bcount)
        {
            int nn=S.lastIndexOf(".");
            int n=N-1-nn;
            answer=bcount-n;
        }else if (count == N)
        {
            count = 0;
        }else
        {
            answer=count;
        }

        //System.out.println(test);
        //Collections.sort(a);
        //System.out.println(Arrays.toString(list1.toArray()));
        //System.out.println(Arrays.toString(array1));
		//System.out.println(Arrays.deepToString(a));
        System.out.println(answer);
    }
}