#include <fstream>
using namespace std;

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

int e[1000001];
long long s;
int main()
{
    int n,i,j;
    in >> n;

    for (i=1;i<=n;i++)
        e[i]=i;

    for (i=2;i<=n;i++)
       if (e[i]==i)
            for (j=i;j<=n;j+1=i)
                e[j]=e[j]/i*(i-1);

    for (i=2;i<=n;i++)
        s+=e[i];

    out << 2*s+1;

    return 0;
}