import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
        int n=sc.nextInt();
        String [] s=sc.next().split("");
        String [] t=sc.next().split("");
        int count=0;

        for(int i=0; i<n; i++){
            if(!(s[i].equals(t[i]))){
                count++;
            }
        }
        System.out.println(count);
        sc.close();
	}
}