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.Linq;

class Program {
    static void Main (string[] args) {
        var N = int.Parse (Console.ReadLine ());
        var S = Console.ReadLine ();
        var a = S.Select(x=>x==char.Parse(".")? 0:1).ToArray();
        int cnt =0;

        for(var i =N-1;i>0;i--)
        {
            if(a.Take(i).Sum()>a.Skip(i).Sum())
            {
                if(a[i]==0)cnt++;
            }
            else
            {
                if(a[i]==1)cnt++;
            }
        }
        Console.WriteLine(cnt);
    }
}