#include <fstream>

using namespace std;
ifstream cin("fractii.in");
ofstream cout("fractii.out");
int phi[1000001];
int main()
{
    int n,i,j;
    cin >> n;
    for(i = 2;i <= n;i++){
        phi[i] = i;
    }
    for(i = 2;i <= n;i++){
        if(phi[i] == i){
            for(j = i;j <= n;j+=i){
                phi[j] -= (phi[j] / i);
            }
        }
    }
    long long sum = 0;
    for(i = 0;i <= n;i++){
        sum += phi[i];
    }
    cout << sum * 2 + 1;
    return 0;
}