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;

public class Program
{

	static void Main(string[] args)
	{
		var N = int.Parse(Console.ReadLine());
		var S = Console.ReadLine();
		var flag = false;
		var black = 0;
		var white = 0;

		for(int i=0;i<N;i++)
		{
			if (S[i] == '#')
				flag = true;

			if(flag )
			{
				if (S[i] == '.')
					white++;
				else
					black++;
			}

		}

		if(white > black)
		{
			if(S[N - 1] == '#')
				Console.Write(black - 1);
			else
				Console.Write(black);
		}
		else
		{
			Console.Write(white);
		}
	}
}