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;

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


            //テンプレート
            //// 整数の入力
            //int a = int.Parse(Console.ReadLine());
            //// スペース区切りの整数の入力
            //string[] input = Console.ReadLine().Split(' ');
            //int b = int.Parse(input[0]);
            //int c = int.Parse(input[1]);
            //// 文字列の入力
            //string s = Console.ReadLine();
            ////出力
            //Console.WriteLine(a + b + c + " " + s);

            int n = int.Parse(Console.ReadLine());
            string s = Console.ReadLine();

            char[] s_char = s.ToCharArray();

            //goal
            int count = 0;
            int count_black = 0;

            //
            char before_color = ' ';
            bool flg = true;

            foreach (var c in s_char) {

                var current_color = c;

                if (current_color == '#')
                {
                    count_black++;
                }

                if ((current_color == '.' && before_color == '#') && flg)
                {
                    count++;
                    flg = false;
                }
                else if(current_color == '.' && flg == false)
                {
                    count++;
                }
                    

                before_color = c;
            }

            if (count <= count_black)
                Console.WriteLine(count);
            else
                Console.WriteLine(count_black);

        }
    }
}