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.*;
public class Main {

  public static void main(String[] args) { 
      Scanner sc = new Scanner(System.in);
      int n = sc.nextInt();
      String s = sc.next();
      int cnt = 0;
      for(int i = 0; i < s.length();) {
        if(s.charAt(i) == '.') { i++; continue; }

        int cntBlack = 0;
        while(i < s.length() && s.charAt(i) == '#') {
          cntBlack++; i++;
        }
        int cntWhite = 0;
        while(i < s.length() && s.charAt(i) == '.') {
          cntWhite++; i++;
        }
        cnt += Math.min(cntBlack, cntWhite);
      }
      System.out.println(cnt);
  }
}