using System;

namespace yukicoder
{
    class Program
    {

        static void Main(string[] args)
        {
            int n = int.Parse(Console.ReadLine());
            var S = Console.ReadLine();
            var T = Console.ReadLine();
            int count = 0;
            //string[] strings1= new string[n];
            //string[] strings2 = new string[str.Length];

            for(int i = 0; i < n; i++)
            {
                if(S.Substring(i , 1) == T.Substring(i , 1))
                {
                    continue;
                }
                else if (!(S.Substring(i, 1) == T.Substring(i, 1)))
                {
                    count++;
                }
            }
            Console.WriteLine(count);     
        }
    }
}