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) {
		int N,K;
		String S;
		Scanner sc=new Scanner(System.in);	
		N=sc.nextInt();
		S=sc.next();
		char c[]=S.toCharArray();
		int num=0;
		
		for(int i=1;i<N;i++) {
				
					if(i!=N-1) {
						if(c[i-1]=='#'&&c[i]=='.') {
						c[i-1]='.';
					    if(i-2>1) {
					    	i=i-2;
					    }
						num++;
						
						
					}
					}
					
					
			}
			
		
			
		System.out.println(num);
	}
}