import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int n, count = 0;
        String S, T;

        n = sc.nextInt();
        S = sc.next();
        T = sc.next();

        while (n < 1 || n > 1000) {
            n = sc.nextInt();
        }

        while (!(S.length() == n || T.length() == n)) {
            System.out.println("Taking input again");
            S = sc.next();
            T = sc.next();
        }

        String[] original = S.split("");
        String[] arrayT = T.split("");

        for (int i = 1; i < arrayT.length; i++) {
            if (original[i].equalsIgnoreCase(arrayT[i])) {
                
            } else {
                count++;
            }

        }
        System.out.println(count);

    }
}