#include <fstream>

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

int nrNrPrime[1000005];

void preprocEratosGen(int n)
{
    int i, j;
    nrNrPrime[1] = 1;
    for(i = 2; i <= n; i++)
        nrNrPrime[i] = i - 1;

    for(i = 2; i <= n; i++)
        for(j = 2; j*i <= n; j++)
            nrNrPrime[i * j] -= nrNrPrime[i];
}

int main()
{
    int N, i;
    long long rasp = 1;

    fin >> N;

    preprocEratosGen(N);

    for(i = 1; i <= N; i++)
        rasp += 2*nrNrPrime[i];
    fout << rasp;

    return 0;
}