import java.util.*;

class Main {
	static Scanner sc = new Scanner(System.in);
	public static void main(String[] args) {
		
		int n = sc.nextInt();
		String s = sc.next();
		String t = sc.next();
		int ans = 0;
		for (int i=0; i<n; i++) {
			if (s.charAt(i) != t.charAt(i)) ans++;
		}
		System.out.println(ans);
		
		
	}
}