левенштейн

using System;
using System.Text;
using System.Collections.Generic;
using System.Text.RegularExpressions;

class MainClass
{
  static int Minimum(int a, int b, int c)
 {
   int min = 0;

   if (a <= b && a <= c)
    min = a;
   else if (b <= a && b <= c)
    min = b;
   else if (c <= a && c <= b)
    min = c;
   return min;
 }

  public static string Replace_s(string str)
  {
    Regex regF = new Regex(@"[^a-z0-9\s]");
            str = regF.Replace(str.ToLower(), string.Empty);

            MatchCollection regS = Regex.Matches(str, @"[a-z0-9]{4,}\s?");

            str = "";
            foreach (Match match in regS)
            {
              str += match.Value;
            }

            return str;
  }

  public static int Levenstain(string firstString, string secondString)
  {
   int result;
   int n = firstString.Length + 1;
   int m = secondString.Length + 1;
   int [,] mass = new int[n,m];

   for(int i = 0; i < n; i++)
    mass[i,0] = i;

  for(int j = 0; j < m; j++)
   mass[0,j] = j;

  for(int i = 1; i < n; i++)
     for (int j = 1; j < m; j++)
     {
      int toReplace = 0;

      if (secondString[j-1] == firstString[i-1])
       toReplace = 0;
       else toReplace = 1;

      mass[i, j] = Minimum(mass[i-1, j] + 1, mass[i,j-1] + 1, mass[i-1, j-1] + toReplace);
     }


   result = mass[n-1,m-1];
   return result;
  }
  public static void Main(string[] args)
  {
    string firstString;
    string secondString;

    firstString = Console.ReadLine();
    secondString = Console.ReadLine();
     firstString = Replace_s(firstString);
     secondString = Replace_s(secondString);

    Console.WriteLine(Levenstain(firstString, secondString));
}
}