public class No_224 {

	public static void main(String[] args) {
		java.util.Scanner sc = new java.util.Scanner(System.in);
		int n = sc.nextInt();
		String S = sc.next();
		String T = sc.next();
		char Sc;
		char Tc;
		int count = 0;

		for (int i = 0; i < n; i++) {
			Sc = S.charAt(i);
			Tc = T.charAt(i);
			if (Sc != Tc) {
				count++;
			}
		}
		System.out.println(count);

	}

}