import java.util.Scanner;
public class Main{
	private static Scanner sc=new Scanner(System.in);
	public static void main(String args[])throws Exception{
		int n=Integer.parseInt(sc.nextLine());
		char s[]=sc.nextLine().toCharArray(),t[]=sc.nextLine().toCharArray();
		n=0;
		for(int i=0;i<s.length;i++){
			if(s[i] != t[i]){
				n++;
			}
		}System.out.println(n);

	}
}