#include <fstream>
using namespace std;
ifstream cin("fractii.in");
ofstream cout("fractii.out");
int n,phi[1000000];
long long ans;
int main()
{
    cin>>n;
    for (int i=1;i<=n;i++)
        phi[i]=i-1;
    for (int i=1;i<=n/2;i++)
        for (int j=2;i*j<=n;j++)
           phi[i*j]-=phi[i];
    for (int i=2;i<=n;i++)
        ans+=2*phi[i];
    ans++;
    cout<<ans;
    return 0;
}