import java.util.Scanner;
public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        String s = sc.nextLine();
        String t = sc.nextLine();

        int count=0;
        for(int i=0 ; i<n ; i++){
            if(s.charAt(i)!=t.charAt(i)){
                count++;
            }
        }

        System.out.println(count);

    }
}