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 scan=new Scanner(System.in);
		int a=scan.nextInt();
		String str=scan.next();
		int rui[]=new int[a];
		int co=0;
		for(int i=0;i<a;i++) {
			char ch=str.charAt(i);
			if(ch=='#') {
				co++;
			}
			rui[i]=co;
		}
		if(rui[a-1]==a) {
			System.out.println(0);
			return;
		}
		int ans=1145141919;
		int len=str.length();
		for(int i=0;i<str.length();i++) {
			int change=rui[i];
			int nokori=len-i-1;
			int zerosum=rui[a-1]-rui[i];
			change+=nokori-zerosum;
			if(ans>change) {
				ans=change;
			}
		}
		System.out.println(ans);
	}
}