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: Time Limit Exceeded)

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();
		sc.close();
		int cnt = Integer.MAX_VALUE;
		int bcnt = 0;
		int wcnt = 0;
		for(int i = 0;i <= N;i++) {
			String s1 = S.substring(0,i);
			String s2 = S.substring(i, S.length());
			for(int j = 0;j<s1.length();j++) {
				if(s1.charAt(j)=='#') {
					bcnt++;
				}
			}
			for(int k = 0;k<s2.length();k++) {
				if(s2.charAt(k)=='.') {
					wcnt++;
				}
			}
			cnt = Math.min(cnt, bcnt+wcnt);
			bcnt=0;wcnt=0;
		}
		System.out.println(cnt);
	}
}