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.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {
	public static void main(String args[]) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

		int n = Integer.parseInt(br.readLine());

		String str[] = br.readLine().split("");

		int bCount = 0;
		int wCount = 0;

		for (int i = 0; i < n; i++) {
			if (str[i].equals("#")) {
				bCount++;
			} else {
				wCount++;
			}
		}

		int ans = 0;

		if (wCount > bCount) {
			for (int i = 0; i < n; i++) {
				if (str[i].equals("#")) {
					if (i + 1 < n) {
						if (str[i + 1].equals(".")) {
							ans++;
						}
					}
				}
			}
		} else {
			for (int i = 0; i < n; i++) {
				if (str[i].equals("#")) {
					if (i + 1 < n) {
						if (str[i + 1].equals(".")) {
							ans++;
						}
					}
				}
			}
		}
		System.out.println(ans);
	}
}