#include <fstream>

using namespace std;

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

long long n,k,v[1000010];

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

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