using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace template
{
    class Program
    {
        static void Main(string[] args)
        {
            int n = int.Parse(Console.ReadLine());
            string s1 = Console.ReadLine();
            string s2 = Console.ReadLine();
            int ret = 0;
            for (int i = 0; i < n; i++)
            {
                if (s1[i] != s2[i]) ret++;
            }
            Console.WriteLine(ret);
        }
    }
}