Swayamvar

//This is The Coding Area
import java.util.*;
import java.lang.*;
import java.io.*;
class Swayamvar{

   public static void main(String[] args){
      try{
        BufferedReader inp = new BufferedReader (new InputStreamReader(System.in));
        int N= Integer.parseInt(inp.readLine());
        String bride = inp.readLine();
        String groom = inp.readLine();
        List<Character>  brides = convertStringToCharList(bride);
        List<Character>  grooms = convertStringToCharList(groom);
        
       int i =0,count =0;
        while(i<brides.size())
        {
            int j=0;
          while(j<grooms.size()){
             boolean res = brides.get(i).equals(grooms.get(0));
             if(res){
                 count++;
                 grooms.remove(0);
                 break;
             }
            else if(res == false){
              Collections.rotate(grooms, 1);
              j++; 
            }
          }
          i++;
          if(i>count)
            break;
        }
       System.out.print(N-count);
      }
     catch(Exception e){
         return;
     }
   
   }
   public static List<Character> 
    convertStringToCharList(String str) 
    { 
        List<Character> chars = new ArrayList<>(); 
        for (char ch : str.toCharArray()) { 
            chars.add(ch); 
        } 
        return chars; 
    } 


}