#include <fstream>

using namespace std;

int main()
{
    ifstream in("fractii.in");
    ofstream out("fractii.out");
    int n, i, j, v[100];
    in >> n;
    for(i=1;i<=n;i++) v[i]=n;
    for(i=2;i<=n;i++)
        if(v[i]==i)
        for(j=i;j<=n;j+=i) v[j]=v[j]/i*i*(i-1);
    int s = 0;
    for(i=2;i<n;i++) s+= v[i];
    out << 2*s + 1;
    return 0;
}