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.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 countW = 0;
		int countB = 0;
		int countC = 0;
		String black = "#";
		String white = ".";
		int ans = 0;

		for (int i = s.indexOf(black) - 1; i < s.length(); i ++) {
			if (String.valueOf(s.charAt(i)).equals(white)) {
				countW++;
				if (String.valueOf(s.charAt(i - 1)).equals(black)) {
					countC++;
				}
			}
		}
		if (countC != 0) {
			ans = Math.min(countW, n - countW - s.indexOf(black));
		}
		System.out.println(ans);
	}

}