using System;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static void Main(string[] args)
    {
        int n = int.Parse(Console.ReadLine());
        string before = Console.ReadLine();
        string after = Console.ReadLine();
        int count = 0;

        for (int i = 0; i < n; i++)
        {
            if (before[i] != after[i])
            {
                count++;
            }
        }

        Console.WriteLine(count);
        Console.Read();
    }
}