#include <fstream>
#define NMAX 1000010

using namespace std;

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

bool C[NMAX];
int N, A, NF;

int main()
{
    int i, j, a;
    fin >>N;
    A = 1, NF = 1, a = 0;
    for (i = 2; i <= N; i++)
        if (C[i] == 0)
        {
            for (j = i; j <= N; j+=i)
                if (C[j]==0)
                    a++, C[j] = 1;
            NF += (A-(N/i-a))*a*2;
            A += a;
            a = 0;
        }
   fout <<NF;
   fout.close();
   return 0;
    
}