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

class No713{
    static void Main(){
        var a=Int32.Parse(Console.ReadLine());
        if(a==1){
            Console.WriteLine(0);
            return;
        }
        List<int>list=new List<int>();
        list.Add(2);
        for(int i=3;i<a+1;++i) if(i%2!=0)list.Add(i);
        var b=2;
        for(int i=1;i<list.Count;++i){
            for(int j=i+1;j<list.Count;++j){
                if(i==list.Count-1)break;
                if(list[j]%list[i]==0)list.Remove(list[j]);
            }
            b+=list[i];
        }
        Console.WriteLine(b);
    }
}