import java.util.*;

public class Run {
    public static void main (String arg[]) {
        Scanner scan = new Scanner(System.in);
        int ans = 0;

        int length = scan.nextInt();
        String S = scan.next();
        String T = scan.next();

        for (int i = 0; i < length; i++) {
            if (!S.substring(i, i+1).equals(T.substring(i, i+1))) ans++;
        }
        System.out.println(ans);
    }
}