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.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApp5
{

    class Program
    {
        static void Main(string[] args)
        {

            int N = int.Parse(Console.ReadLine());
            string S = Console.ReadLine();
            int WP = N + 1;
            int BP = -1;


            for (int i = 0; i < N; i++)
            {
                if (S[i] == '.' && i < WP)
                {
                    WP = i;
                }
                else if (S[i] == '#' && i > BP)
                {
                    BP = i;
                }

            }

            int resW = 0;
            int resB = 0;

            for (int i = 0; i <= BP; i++)
            {
                if (S[i] == '#')
                {
                    resB++;
                }
            }
            for (int i = N - 1; i >= WP; i--)
            {
                if (S[i] == '.')
                {
                    resW++;
                }
            }

            if (resW >= resB)
            {
                Console.WriteLine(resB);
            }
            else
            {
                Console.WriteLine(resW);
            }


        }
    }
}