#include <fstream>

using namespace std;
ifstream cin("fractii.in");
ofstream cout("fractii.out");

int phi[1000005],n;
long long s;
int main()
{
    cin>>n;
    for(int i=1;i<=n;i++)phi[i]=i;
    for (int i=2;i<=n;i++)
        if (phi[i]==i){
            phi[i]=i-1;
            for (int j=2*i;j<=n;j+=i)phi[j] = phi[j] / i * (i - 1);
        }
    for (int i=1;i<=n;i++)s+=phi[i];
    cout<<s*2-1;
    return 0;
}