using System;
using static System.Console;
using System.Linq;
using System.Collections.Generic;

class Program
{
    static int NN => int.Parse(ReadLine());
    static int[] NList => ReadLine().Split().Select(int.Parse).ToArray();
    public static void Main()
    {
        Solve();
    }
    static void Solve()
    {
        var n = NN;
        var isprime = Enumerable.Repeat(true, n + 1).ToArray();
        var ans = 0;
        for (var i = 2; i <= n; ++i)
        {
            if (isprime[i])
            {
                ans += i;
                for (var j = i * 2; j <= n; j += i) isprime[j] = false;
            }
        }
        WriteLine(ans);
    }
}