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;

public class Program
{
    public static void Main()
    {
        
        var num=int.Parse(Console.ReadLine());
        var line=Console.ReadLine();
        
        var count1=0;
        var x=0;
        for(var i=0;i<num;i++){
            if(line[i]=='#')x=1;
            if(x==1&&line[i]=='.')count1+=1;
        }
        var count2=0;
        var y=0;
        for(var i=num-1;i>=0;i--){
            if(line[i]=='.')y=1;
            if(y==1&&line[i]=='#')count2+=1;
        }
        var count=count1;
        if(count2<count1)count=count2;
        
        if(count1==0||count2==0)Console.WriteLine(0);
        else Console.WriteLine(count);
        
    }
}