using System;
public class Program
{
    public static void Main()
    {
        int num = int.Parse(Console.ReadLine() ?? string.Empty);
        //string[] str = (Console.ReadLine() ?? string.Empty).Trim().Split(' ');
        string str = Console.ReadLine() ?? string.Empty;
        string str2 = Console.ReadLine() ?? string.Empty;

        int count = 0;
        for (int i = 0; i < num; i++)
        {
            if (str[i] != str2[i])
            {
                count++;
            }
        }
        Console.WriteLine(count);
    }
}