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) {
		// TODO 自動生成されたメソッド・スタブ

		Scanner sc1 = new Scanner(System.in);

		int n = sc1.nextInt();
		String s = sc1.next();

		int a = 0;
		int b = 0;

		boolean flag = true;

		for ( int i = 0 ; i < n ; i++) {
			if ( flag ) {
				if (s.charAt(i) == '#') {
					flag = false;
				}
			}

			else if ( s.charAt(i) == '.' ) {
				a++;
			}
			else {
				b++;
			}
		}

		if ( a > b ) {
			System.out.println(b);
		}
		else {
			System.out.println(a);
		}

		sc1.close();

	}

}