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();
		sc.close();

		long cnt = Long.MAX_VALUE;
		long bcnt = 0;
		long wcnt = S.chars().filter(ch -> ch == '.').count();
		for(int i = 0;i < N;i++) {
			if(S.charAt(i)=='#') {
				bcnt++;
			}else if(S.charAt(i)=='.') {
				wcnt--;
			}
			cnt = Math.min(cnt, bcnt+wcnt);
		}
		bcnt = S.chars().filter(ch -> ch == '#').count();
		wcnt = 0;
		cnt = Math.min(cnt, bcnt+wcnt);
		System.out.println(cnt);
	}
}