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.Collections;
import java.util.Scanner;

public class Main {
	public static String repeat(String str, int n) {
		return String.join("", Collections.nCopies(n, str));
	}

	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		sc.nextLine();
		String line = sc.nextLine();

		int diff = 0;
		String rightAnswer = repeat(".", n);
		int nextDiff = 0;

		for (int i = 0; i < n; i++) {
			if (line.charAt(i) != rightAnswer.charAt(i))
				diff++;
		}

		int best = diff;

		for (int i = n - 1; i > -1; i--) {
			if (line.charAt(i) == '#')
				nextDiff = diff - 1;
			else {
				nextDiff = diff + 1;
			}
			if (nextDiff < best) {
				best = nextDiff;
			}
		}

		System.out.println(best);

		sc.close();
	}
}