using System;

public class Program {
	public static void Main(string[] args) {
		Console.ReadLine(); // n
		char[] a = Console.ReadLine().ToCharArray();
		char[] b = Console.ReadLine().ToCharArray();
		
		int count = 0;
		
		for (int i = 0; i < a.Length; i++) {
			if (!a[i].Equals(b[i])) {
				count++;
			}
		}
		
		Console.WriteLine(count);
	}
}