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

namespace foryuki
{
    class Program
    {
        static void Main(string[] args)
        {
            int n = int.Parse(Console.ReadLine());
            char[] S = Console.ReadLine().ToCharArray();
            char[] T = Console.ReadLine().ToCharArray();
            int cnt = 0;

            for (int i = 0; i < n; i++)
            {
                if (S[i] == T[i])
                {
                    cnt++;
                }
            }

            Console.WriteLine(n - cnt);
        }

        //-------------------------------------------------------------

        static int[] ConvertStringArrayToIntArray(string[] array)
        {
            return Array.ConvertAll(array, str => int.Parse(str));
        }

        static List<int> ConvertStringArrayToIntList(string[] str)
        {
            var list = new List<int>();
            foreach (var c in str)
            {
                list.Add(int.Parse(c));
            }
            return list;
        }
    }
}