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_array = sc.next().split("");
    int output = 0;
    boolean border = false;
    for(int i=1; i<n; i++){
      if(s_array[i-1].equals("#") && s_array[i].equals(".")){
        if(i == n -1){
          output++;
        }else if(!s_array[i-1].equals(s_array[i+1])){
          output++;
          s_array[i-1] = s_array[i];
        } else if(s_array[i-1].equals(s_array[i+1])){
          output++;
          s_array[i] = s_array[i-1];
        }
      }
    }
    System.out.println(output);
  }
}