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 scanner = new Scanner(System.in);

    int N = scanner.nextInt();
    char[] s = scanner.next().toCharArray();

    int[] numb = new int[N];
    int[] numw = new int[N];
    int countb = 0;
    for (int i = 0; i < N; i++) {
      numb[i] = countb;
      if (s[i] == '#') {
        countb++;
      }
    }
    int countw = N - countb;
    if (countb == 0 || countw == 0) {
      System.out.println(0);
      return;
    }

    for (int i = 0; i < N; i++) {
      numw[i] = countw;
      if (s[i] == '.') {
        countw--;
      }
    }

    int min = N;
    for (int i = 0; i < N; i++) {
      if (s[i] == '#') {
        min = Math.min(min, numb[i] + numw[i]);
      }
    }
    System.out.println(min);
  }
}