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) {

		try (Scanner sc = new Scanner(System.in)) {
			int N = Integer.parseInt(sc.next());
			String S = sc.next();
			
			final char w = '.';
			final char b  = '#';
			int count = 0;
			for(int i = 1; i < S.length(); i++) {
				if(w == S.charAt(i -1) && S.charAt(i -1) != S.charAt(i)) {
					count++;
					continue;
				}
			}
			if(b == S.charAt(N -2) && S.charAt(N -2) != S.charAt(N -1)) {
				count++;
			}
			System.out.println(count);
		} // Scanner Close
	}
}