#include<fstream>

#define NMAX 1000000

using namespace std;


int phi[NMAX + 1];

int main() {

    int N;

    ifstream f("fractii.in");
    ofstream g("fractii.out");

    f >> N;
    for (int i = 2; i <= N; i++) {
        phi[i] = i - 1;
    }
    for (int i = 2; i <= N/2; i++) {
        for (int j = 2 * i; j <= N; j += i) {
            phi[j] -= phi[i];
        }
    }

    long long numFrac = 1;

    for (int i = 2; i <= N; i++) {
        numFrac += 2 * phi[i];
    }

    g << numFrac;
    
    return 0;
}