package m.shin;
import java.util.Scanner;
public class Con224 {

	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		int n = s.nextInt();
		String S = s.next() , T = s.next();
		s.close();

		int count = 0;
		for(int i = 0;i < S.length();i++){
			if(S.charAt(i) != T.charAt(i)){
				count++;
			}
		}
		System.out.println(count);
	}

}