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 C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;

class myon
{
    public static void Main(string[] args)
    {
        var myon = new myon();
    }

    public myon()
    {
        int N = int.Parse(Console.ReadLine());
        string S = Console.ReadLine();

        char[] Slist = new char[N];
        for (int i = 0; i < N; i++)
        {
            Slist[i] = S[i];
        }

        List<int> results = new List<int>();

        int eaB = 0;
        int laW = 0;


        int bcount = 0;
        int wcount = 0;
        for (int i = 0; i < N; i++)
        {
            if (Slist[i] == '#') bcount++;
            else wcount++;
        }
        results.Add(bcount);
        results.Add(wcount);



        for (int i = 0; i < N; i++)
        {
            if (Slist[i] == '#')
            {
                eaB = i;
                break;
            }
        }

        for (int i = 0; i < N; i++)
        {
            if (Slist[i] == '.')
            {
                laW = i;
            }
        }



        int Bc = 0;



        for (int i = eaB; i <= laW; i++)
        {
            if (Slist[i] == '#') Bc++;
        }

        int Count = 0;
		int Wc =(laW - eaB + 1)-Bc ;
        int pos = laW;
        while (Wc>1)
        {
            if (Slist[pos] == '.')
            {
                Count += 2;
                Wc--;
                pos--;
            }
        }

        results.Add(Count);




        Console.WriteLine(results.Min());

    }
}