#include <fstream>

using namespace std;

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

long long n,k,phi[1000010];

int main() {
    f>>n;
    for (int i=1;i<=n;i++) phi[i]=i;

    for (int i=2;i<=n;i++)
        if (phi[i]==i)
            for (int j=i;j<=n;j+=i) phi[j] /=i, phi[j] *= (i-1);
    for(int i=2;i<=n;i++)
        k+=phi[i];
    g<<2*k+1;
}