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