#include<fstream>
#include<vector>
using namespace std;
ifstream in("fractii.in");
ofstream out("fractii.out");
vector <int> PrimeNumbers;
const int NMax = 1000000;
int N, Phi[NMax+5];
long long Sol;

void ComputePhi() {
    for(int i = 2;i <= N;i++)
        Phi[i] = i;
    Phi[1] = 0;
    for(int i = 2;i <= N;i++) {
        if(Phi[i] == i) {
            for(int j = i;j <= N;j += i) {
                Phi[j] /= i;
                Phi[j] *= i - 1;
            }
        }
    }
}

int main() {
    in >> N;
    ComputePhi();
    for(int i = 2; i <= N; i++)
        Sol += 2 * Phi[i];
    out << Sol + 1 << '\n';
}