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.io.PrintWriter;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        try (InputReader in = new InputReader(); PrintWriter out = new PrintWriter(System.out)) {
            new Main().solve(in, out);
            out.flush();
        }
    }

    void solve(InputReader in, PrintWriter out) {
        int n = in.nextInt();
        char[] s = in.next().toCharArray();
        int w = 0;
        int b = 0;
        int t = 0;
        boolean flag = false;
        for (int i = 0; i < n; i++) {
            char c = s[i];
            if (c == '.') {
                b++;

                if (flag) {
                    t++;
                }
            }

            if (c == '#') {
                w++;
                flag = true;
            }
        }

        flag = false;
        int t2 = 0;
        for (int i = n - 1; i >= 0; i--) {
            char c = s[i];
            if (c == '#') {
                if (flag) {
                    t2++;
                }
            }

            if (c == '.') {
                flag = true;
            }
        }

        out.println(Math.min(w, Math.min(b, Math.min(t, t2))));
    }
}

class InputReader implements AutoCloseable {
    private final Scanner sc = new Scanner(System.in);

    String next() {
        return this.sc.next();
    }

    int nextInt() {
        return Integer.parseInt(this.sc.next());
    }

    long nextLong() {
        return Long.parseLong(this.sc.next());
    }

    double nextDouble() {
        return Double.parseDouble(this.sc.next());
    }

    @Override
    public void close() {
        this.sc.close();
    }
}