import java.util.Scanner;

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

		int ans = 0;
		for(int i = 0; i < n; i++) {
			char c1 = S.charAt(i);
			char c2 = T.charAt(i);
			if(c1 != c2) {
				ans ++;
			}
		}
		System.out.println(ans);
	}
}