import java.util.*;

public class Yukicoder224{
	public static void main(String[] args){
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		String s = scan.next();
		String t = scan.next();
		int kazu = 0;
		for(int i = 0;i < n;i++){
			if(s.charAt(i) != t.charAt(i))	kazu++;
		}
		System.out.println(kazu);
	}
}