#include <fstream>
#include <cmath>
using namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");
unsigned int n,p,k,cp,C[1000001];
unsigned long long s;
/*void Ciur()
{
    C[0]=C[1]=1;
    for(unsigned int i=2;i*i<=n  ;i++)
        if(C[i]==0)
            for(unsigned int j=i*2;j<=n;j+=i)
            C[j]=1;
}
*/
int main()
{
    fin>>n;
   // Ciur();
    for(unsigned int i=1; i<=n; i++)
    {
        if(i==1)
            s+=1;
        //else if(C[i]==0)
            //s+=i-1;
        else
        {
            cp=i;
            p=2;
            k=0;
            while(cp>1)
            {
                while(cp%p==0)
                {
                    k++;
                    cp=cp/p;
                }
                s=s+(p-1)*pow(p,k-1);

                p++;
            }
        }

    }
    fout<<s*2-1;
    return 0;
}