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();
        
        int white=0;
        int black=0;
        for (int index=0; index<N; index++){
            if (S.charAt(index)=='#'){
                black++;
            } else {
                white++;
            }
            
        }
        
        int min;
        if (white>black){
            min=black;
        } else {
            min=white;
        }
        int count = 0;
        boolean flag = true;
        for (int index=0; index<N; index++){
            if (flag){
                if (S.charAt(index)=='#'){
                    flag=false;
                }
            } else {
                if (S.charAt(index)=='.'){
                    count++;
                }
            }
        }
        
        if (min>count){
            System.out.println(count);
        } else {
            System.out.println(min);
        }
    }
}