#include <fstream>

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

const int nmax=1000010;
long long p[nmax];

int main()
{
    long long n=0,i=0,j=0,x=1;
    f>>n;
    for (i=1; i<=n; ++i)
        p[i]=i;
    for (i=2; i<=n; ++i)
    {
        if (p[i]==i)
            for (j=i; j<=n; j+=i)
                p[j]=(p[j]/i)*(i-1);
        x+=2*p[i];
    }

    g<<x;
    return 0;
}