#include<fstream>
using namespace std;
ifstream fi("fractii.in");
ofstream fo("fractii.out");
long long n,i,A[1000001],j,rez;
int main()
{
    fi>>n;
    rez=1;
    for(i=1; i<=n; i++)
    {
        A[i]=A[i]+i-1;
        rez=rez+2LL*A[i];
        for(j=2*i; j<=n; j+=i)
        {
            A[j]-=A[i];
        }
    }
    fo<<rez<<"\n";
    fi.close();
    fo.close();
    return 0;
}