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 = Integer.parseInt(sc.nextLine());
    String S = sc.nextLine();
    int n1 = 0, n2 = 0;
    boolean f = false;
    for(int i = 0; i < N; i++){
      char c = S.charAt(i);
      if(f && c == '.'){
        n1++;
      }else if(c == '#'){
        f = true;
        n2++;
      }
    }
    int count = 0;
    for(int i = S.length()-1; i >= 0; i--){
      if(S.charAt(i) == '#'){
        count++;
      }else{
        break;
      }
    }
    n2 -= count;
    
    System.out.println(Math.min(n1, n2));
  }
}