using System;
using System.Collections.Generic;
using System.Linq;
using System.Numerics;
class Program
{
    static void Main()
    {
        int i = 0;
        int n = int.Parse(Console.ReadLine());
        string a = Console.ReadLine();
        string b = Console.ReadLine();
        for(int X = 0; X < n; X++)
        {
            if (a[X] != b[X])
            {
                i++;
            }
        }
        Console.WriteLine(i);
    }
}