using System;

public class Hello
{
    public static void Main()
    {
        var n = int.Parse(Console.ReadLine().Trim());
        var s = Console.ReadLine().Trim();
        var t = Console.ReadLine().Trim();
        var count = 0;
        for (int i = 0; i < n; i++)
            if (s[i] != t[i]) count++;
        Console.WriteLine(count);
    }
}