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

namespace YukiCoder
{
    class Program
    {
        static void Main(string[] args)
        {
            int N = int.Parse(Console.ReadLine());
            var pr = new List<int>() { 0 };
            var pa = Enumerable.Range(2, N - 1).ToList();
            for (int k = 1; k * k < N; )
            {
                k = pa[0];
                pr.Add(k);
                pa.RemoveAll(x => x % k == 0);
            }
            pr.AddRange(pa);
            Console.WriteLine(pr.Sum());
            Console.ReadLine();
        }
    }
}