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