#include<fstream>
using namespace std;
ifstream in("fractii.in");
ofstream out("fractii.out");
int v[1000001],n;
unsigned long long suma=0;

int main ()
{
    int i,j;
    in>>n;
    for(i=2;i<=n;++i)
        v[i]=i-1;
    for(i=2;i<=n;++i)
    {
        suma+=v[i];
        for(j=2*i;j<=n;j+=i)
            v[j]-=v[i];
    }
    out<<suma*2+1<<'\n';
    return 0;
}