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 scanner = new Scanner(System.in);
		int N = scanner.nextInt();
		String S = scanner.next();
		// N == S.length();
		boolean flag = false;
		int ans = 0;
		for (int i = 0; i < N; i++) {
			if (S.charAt(i) == '#') {
				flag = true;
			}
			if (flag == true && S.charAt(i) == '.') {
				ans++;
			}
		}
		flag = false;
		int ans2 = 0;
		for (int i = N - 1; i >= 0; i--) {
			if(S.charAt(i) == '.') {
				flag = true;
			}
			if(flag == true && S.charAt(i) == '#') {
				ans2 ++;
			}
		}
		System.out.println(Math.min(ans, ans2));
		scanner.close();
	}
}