#include<fstream>

using namespace std;

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

const int Nmax  = 1000009;

int N;long long NumberR; int Phi[Nmax];


int main(){

    fin >> N;
    for(int i = 1; i <= N; ++i)
        Phi[i] = i - 1;

    for(int i = 2; i <= N; ++i)
        for(int j = i + i; j <= N; j+= i)
            Phi[j] -= Phi[i]; // j /i = multiplu comun > 1

    for(int i = 2; i <= N; ++i)
        NumberR += Phi[i];
    fout <<  1 + (NumberR << 1);

    return 0;
}