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;

namespace CSsample
{
    class Program
    {
      int rev(string S, int point)
            {
                int num = 0;
                for(int i = 0; i < S.Length; i++)
                {
                    if (i < point)
                    {
                        if(S[i] == '#')
                        {
                            num++;
                        }
                    }
                    else
                    {
                        if(S[i] == '.')
                        {
                            num++;
                        }
                    }
                }
                return num;
            }
        static void Main(string[] args)
        {
          Program obj = new Program();
            int N = int.Parse(Console.ReadLine());
            string S = Console.ReadLine();

            
            int Num = obj.rev(S,0);
            for(int i = 1; i < N; i++)
            {
                if(obj.rev(S,i)<Num)
                {
                    Num = obj.rev(S,i);
                }
            }
            Console.WriteLine(Num);
        }
    }
}