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.InputStreamReader;

public class Main {
	public static void main(String[] args) throws Exception {
//		BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
////		String line = reader.readLine();
//		String[] str = reader.readLine().split(" ");
//		int[] ab = new int[str.length];
//		for (int i = 0; i < str.length; i++) {
//			ab[i] = Integer.parseInt(str[i]);
//		}
//		if ((ab[0] > ab[2] && ab[2] > ab[1]) || (ab[0] < ab[2] && ab[2] < ab[1])) {
//			System.out.println("Yes");
//		}
//		else {
//			System.out.println("No");
//		}
		
//		BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
//		String line = reader.readLine();
//		int N = Integer.parseInt(line);
//		String[] str = reader.readLine().split("");
//		line = reader.readLine();
//		int K = Integer.parseInt(line) -1;
//		String[] re = new String[N];
//		for (int i = 0; i < N; i++) {
//			if (!str[i].equals(str[K])) {
//				re[i] = "*";
//			}
//			else {
//				re[i] = str[i];
//			}
//		}
//		for (int i = 0; i < N; i++) {
//			System.out.print(re[i]);
//		}
//		System.out.println();
		
		
		BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
		String line = reader.readLine();
		int N = Integer.parseInt(line);
		String[] str = reader.readLine().split("");
		int dot = 0;
		int sharp = 0;
		for (int i = 0; i < str.length; i++) {
			if (str[i].equals(".")) {
				dot++;
			}
			else if (str[i].equals("#")) {
				sharp++;
			}
		}
		if (dot == 0 || sharp == 0) {
			System.out.println("0");
		}
		else if (dot >= sharp) {
			System.out.println(sharp);
		}
		else {
			System.out.println(dot);
		}
	}
}