#include <fstream>

using namespace std;

ifstream cin("fractii.in");
ofstream cout("fractii.out");

const int N = 1000000+7;
int phi[N];

int main()
{
    for(int i = 2; i <= N; i++) {
        phi[i] = i-1;
    }

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

    phi[1] = 1;
    //for(int i = 2; i <= 10; i++) cout << phi[i] << " ";

    int n; cin >> n;
    long long int sum = 1;
    for(int i = 2; i <= n; i++) {
        sum += 2*phi[i];
    }

    cout << sum;

    return 0;
}