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 ConsoleApp1
{
    class Program
    {
        static void Main(string[] args)
        {
            int m = int.Parse(Console.ReadLine());
            List<char> str = Console.ReadLine().ToList<char>();


            int strb = new string(str.ToArray()).IndexOf("#");
            //0101010101
            //1011010
            //1000111
            //000111
            //101010101
            //010101010
            //1000111
            //1110000

            int b = str.Count(x => x == '.');
            int w = str.Count(x => x == '#');

            //染まっている
            if (b == 0 || w == 0)
            {
                Console.WriteLine(0);
            }
            else
            {
                int ans = int.MaxValue;
                //黒を入れ替える場合
                if (b <= w)
                {
                    ans = b;

                    //黒の開始位置まで除外
                    if (str[0] == '.') ans -= strb;
                }
                else
                {
                    ans = w;

                    //頭が白
                }
                

                Console.WriteLine(ans);


            }


            //.が白#が黒
            //クロのすぐ右に城が来ないようにしたい


        }

    }
}