import java.util.Scanner;

public class Main {
    static Scanner in = new Scanner(System.in);

    public static void main(String[] args) {
        int N = Integer.parseInt(in.nextLine());
        String s = in.next(), t = in.next();
        int ans = 0;
        for(int i = 0; i < s.length(); i++){
            if(s.charAt(i) != t.charAt(i)){
                ans++;
            }
        }
        System.out.println(ans);
    }
}