import java.util.Scanner;

public class Main {

	/**
	 * @param args
	 */
	public static void main(String[] args) {

		Scanner sc = new Scanner(System.in);
		int num = sc.nextInt();
		String aaa = sc.next();
		String bbb = sc.next();
		int count = 0;
		for (int i = 0; i < num; i++) {
			if (aaa.charAt(i) != bbb.charAt(i)) {
				count += 1;
			}
		}
		System.out.println(count);
	}
}