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;

class Program
{
    static void Main(string[] args)
    {
        // var input = Console.ReadLine().Split().Select(int.Parse).ToArray();
        var N = int.Parse(Console.ReadLine());
        var S = Console.ReadLine().ToArray();

        var ans = 0;

        for(var i = 0; i <S.Length -1; i++)
        {
            var value = S[i];
            var next = S[i + 1];

            if (value == '#' && next == '.')
            {
                if ( i > 0)
                {
                    var previous = S[i - 1];
                    if (previous == '#')
                    {
                        S[i -1] = '.';
                    } else
                    {
                        S[i + 1] = '#';
                    }
                }
                else
                {
                    S[i + 1] = '#';
                }
                ans++;
            }

        }
   
        Console.WriteLine(ans);
    }
}