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: Runtime Error)

import java.util.*;
import java.util.regex.Pattern;

public class Main {
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int N = sc.nextInt();
		String S = sc.next();

		String[] s = S.split("");

		int[] bCnt = new int[N];

		if(s[0].equals("#")){
			bCnt[0] = 1;
		} else {
			bCnt[0] = 0;
		}

		for(int i=1; i<N; i++){
			if(s[i].equals("#")){
				bCnt[i] = bCnt[i-1]+1;
			} else{
				bCnt[i] = bCnt[i-1];
			}
		}

		int[] wCnt = new int[N];
		wCnt[N-1]=0;
		if(s[N-1].equals(".")){
			wCnt[N-2]=1;
		}else{
			wCnt[N-2]=0;
		}

		for(int i=N-3; i>-1; i--){
			if(s[i+1].equals(".")){
				wCnt[i]= wCnt[i+1]+1;
			}else{
				wCnt[i]= wCnt[i+1];
			}
		}

		int min = 999999999;

		for(int i=0; i<N; i++){
			if(min>bCnt[i]+wCnt[i]){
				min = bCnt[i]+wCnt[i];
			}
		}

		System.out.println(min);


	}


}