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;

namespace T1PBC2019C
{
    class MainClass
    {


        static int[] n;

        public static void Main(string[] args)
        {

            n = Array.ConvertAll(Console.ReadLine().Split().ToArray(), int.Parse);
            string s = Console.ReadLine();

            bool blk = false;
            bool wht = false;
            int bcnt = 0;
            int wcnt = 0;
            for(int i = 0; i < n[0]; i++)
            {
                if (!wht)
                {
                    if (s[i] == '#')
                    {
                        wht = true;
                    }
                }
                else
                {
                    if (s[i] == '.')
                    {
                        wcnt++;
                    }
                }

                if (!blk)
                {
                    if (s[n[0] - 1 - i] == '.')
                    {
                        blk = true;
                    }
                }
                else
                {
                    if (s[n[0] - 1 - i] == '#')
                    {
                        bcnt++;
                    }
                }

            }
            Console.WriteLine(Math.Min(wcnt, bcnt));

        }
    }
}