#include <fstream>

using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
unsigned long long n,m,i,j,k,sol,x,p;
int main()
{
    f>>n;
    for(i=2;i<=n;i++)
    {
        int nr=i;
        x=i;
        j=2;
        while(j*j<=x)
        {
            p=0;
            while(x%j==0)
            {
                p++;
                x=x/j;
            }
            if(p!=0)
            {
                nr=nr*(j-1)/j;
            }
            j++;
        }
        if(x>1)
        {
            nr=nr*(x-1)/x;
        }
        sol+=nr*2;
    }
    g<<sol+1;
    return 0;
}