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.*;
import java.lang.*;

public class Main {
    
    public static void main(String args[]){
        Scanner sc = new Scanner(System.in);
        
        int n = sc.nextInt();
        String s = sc.next();
        char[] a = new char[n];
        int cnt = 0;
        for(int i = 0; i < n; i++) {
            a[i] = s.charAt(i);
        }
        String str = "";
        
        
        for (int i = 0; i < n; i++) {
            if (i < n - 1) {
                if (a[i] == '#' && a[i + 1] == '.') {
                    if (i < n - 2) {
                        if (a[i + 2] == '#') {
                            a[i + 1] = '#';
                        } else {
                            a[i] = '.';
                        }
                    } else {
                        a[i + 1] = '#';
                    }
                }
            }
        }
        
        for (int i = 0; i < n; i++) {
            if (a[i] != s.charAt(i)) {
                cnt++;
            }
            //System.out.println(a[i]);
        }
        System.out.println(cnt);
    }
}