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;
using System.Text;

public static partial class Program
{
    public static void Main()
    {
        var n = CRL().ToInt();
        var s = CRL();

        var sP = 0;
        for (int i = 0; i < n; i++)
        {
            if (s[i] == '.')
            {
                sP++;
                continue;
            }

            break;
        }

        var sb = s.Reverse().ToArray();
        var eP = 0;
        for (int i = 0; i < n; i++)
        {
            if (sb[i] == '#')
            {
                eP++;
                continue;
            }

            break;
        }

        var rp = s.Substring(sP, n - sP - eP);
        var count = rp.Count(x => x == '#');
        if (rp.Length - count >= count)
        {
            CWL(count);
        }
        else
        {
            CWL(rp.Length - count);
        }
    }
}

public static partial class Program
{
    //テンプレここから
    public static int ToInt(this string str) => int.Parse(str);
    public static long ToLong(this string str) => long.Parse(str);
    public static long[] ToLong(this IEnumerable<string> strs) => strs.Select(x => x.ToLong()).ToArray();
    public static int[] ToInt(this IEnumerable<string> strs) => strs.Select(x => x.ToInt()).ToArray();
    public static long[] ArrayLongs(this string str, char opr = ' ') => str.Split(opr).ToLong();
    public static int[] ArrayInts(this string str, char opr = ' ') => str.Split(opr).ToInt();
    public static string CRL() => Console.ReadLine();
    public static void CWL(object obj) => Console.WriteLine(obj);
    public static long Diff(long a, long b) => Math.Abs(Math.Max(a, b) - Math.Min(a, b));
    public static long Sign(this long i) => Math.Sign(i);
    public static bool IsEven(this long i) => i % 2 == 0;
    public static bool IsEven(this int i) => i % 2 == 0;
    public static long[] dx = new long[] {0, -1, 0, 1};
    public static long[] dy = new long[] {-1, 0, 1, 0};
    public static long mod = 1000000007;
    public static string alphabet = "abcdefghijklmnopqrstuvwxyz";
    public static long ToLong(this char c) => c.ToString().ToInt();

    public static long[] Sort(this long[] array) => array.OrderBy(x => x).ToArray();
    public static int[] Sort(this int[] array) => array.OrderBy(x => x).ToArray();
    public static long[] DSort(this long[] array) => array.OrderByDescending(x => x).ToArray();
    public static int[] DSort(this int[] array) => array.OrderByDescending(x => x).ToArray();

    public static long GCD(long a, long b) => b == 0 ? a : GCD(b, a % b);

    public static long LCM(long a, long b) => a * b / GCD(a, b);

    //テンプレここまで
}