package yukicoder224;
import java.util.Scanner;
public class Main {
	public static void main(String[] args){
		Scanner sc=new Scanner(System.in);
		int n=sc.nextInt();
		String str1=sc.next();
		String str2=sc.next();
		int count=0;
		for(int i=0;i<n;i++){
			if(str1.charAt(i)!=str2.charAt(i)){
				count++;
			}
		}
		System.out.println(count);
	}
}