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: Accepted)



import java.util.Scanner;


public class Main {
	
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		
		Scanner sc = new Scanner(System.in);
		int N = Integer.parseInt(sc.next());
		char[] stone = sc.next().toCharArray();
		
		int count = 0;
		int ans = Integer.MAX_VALUE;
		for(int i=0;i<N;i++){
			if(stone[i]=='.')count++;
		}
		ans = Math.min(ans,count);
		for(int i=0;i<N;i++){
			if(stone[i]=='.'){
				count--;
			}else{
				count++;
			}
			ans = Math.min(ans,count);
		}

		System.out.println(ans);
		
		sc.close();
	}
	
}