import java.util.Scanner;

public class Test {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		int n = sc.nextInt(), cnt = 0;
		String s1 = sc.next(), s2 = sc.next();
		for(int i = 0; i < n; i++){
			if(s1.charAt(i) != s2.charAt(i)){
				cnt++;
			}
		}
		System.out.println(cnt);
	}
}