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();
		StringBuilder ss = new StringBuilder();
		sc.close();
		ss.append(s);
		int c = 0;
		int d = 0;
		for(int i =1; i<n; i++) {
			if(ss.charAt(i)=='.'&&ss.charAt(i-1)=='#') {
				c++;
				ss.setCharAt(i, '#');
			}
		}
		for(int i =1; i<n; i++) {
			if(ss.charAt(i)=='.'&&ss.charAt(i-1)=='#') {
				d++;
				ss.setCharAt(i, '.');
			}
		}
	
	System.out.println(Math.min(c, d));
	
	
	
	}
}