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

public class Hello
{
    public static void Main()
    {
        var n = int.Parse(Console.ReadLine().Trim());
        if (n == 1) Console.WriteLine(0);
        else
        {
            var a = GeneratePrime(n);
            Console.WriteLine(a.Sum());
        }
    }
    public static List<int> GeneratePrime(int m)
    {
        var pL = new List<int>();
        int p;
        var sqrtMax = Math.Sqrt(m);
        var sL = Enumerable.Range(2, m - 1).ToList();
        do
        {
            p = sL.First();
            pL.Add(p);
            sL.RemoveAll(n => n % p == 0);
        }
        while (p < sqrtMax);
        pL.AddRange(sL);
        return pL;
    }
}