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: Runtime Error)

using System;
					
public class Program
{
	public static void Main()
	{
		//°º¤ø,¸¸,ø¤º°`°º¤ø,¸,ø¤°º¤ø,¸¸,ø¤º°`°º¤ø,¸Kobato Love°º¤ø,¸¸,ø¤º°`°º¤ø,¸,ø¤°º¤ø,¸¸,ø¤º°`°º¤ø,¸
		int a;
		string b;
		a = int.Parse(Console.ReadLine()); 
		b = Console.ReadLine(); 
		int count = 0;
		
		for(int i = 0; i < a-1; i++)
		{
			if(b[i] == '#')
			{
				int x = 0;
				int y = 0;
				bool bo = false;
				while(true)
				{	//Console.WriteLine(x +" "+y);
					if(!bo){
						if(b[i+x+1] == '#')
						{
							x++;
						}
						else
						{
							bo = true;	
						}
					}
					else
					{
						try{
							if(b[i+x+1] == '.')
							{
								x++;
								y++;
							}
							else
							{
								if(y <= x)
								{
									count += y;
								}
								else
								{
									count += x;
								}
								i += x;
								break;
							}
						}
						catch(Exception e)
						{
							if(y <= x)
								{
									count += y;
								}
								else
								{
									count += x;
								}
								i += x;
								break;
						}
					}
				}
			}
		}
		Console.WriteLine(count);
		
		
	}
}