#include <fstream>
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
int n;
long long unsigned nr;
int main()
{
    f>>n;
    nr=2*(n-1)+1;
    for(int i=2;i<n;i++)
        nr+=2*(n-i-n/i+1);
    g<<nr;
    return 0;
}