import java.util.*;

public class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int num = sc.nextInt();
        int cou=0;
        String str1 = sc.next();
        String str2 = sc.next();
        for(int i=0;i<num;i++){
            if(str1.charAt(i) != str2.charAt(i))cou++;
        }
        System.out.println(cou);
    }
}