#include<fstream>

using namespace std;

 int i,j,n;

int t[1000002],k;

int main()
{
ifstream f("fractii.in");
ofstream g("fractii.out");

f>>n;

k=0;
for(i=2;i<=n;i++)
        {
        t[i]+=i-1;
        for(j=i+i;j<=n;j+=i)t[j]-=t[i];
        k+=t[i];
        }

g<<k*2+1;

}