using System;

public class Yuki224
{
	public static void Main()
	{
		Console.ReadLine();
		var s = Console.ReadLine();
		var t = Console.ReadLine();
		
		int cnt = 0;
		
		for (int i = 0; i < s.Length; i++) if(s[i] != t[i]) cnt++;
		
		Console.WriteLine(cnt);
	}
}