#include <iostream>
#include <fstream>

#define ll long long
using namespace std;
ifstream in("fractii.in");
ofstream out("fractii.out");

const int NMax = 1e6 + 5;

int N;
bool notPrime[NMax];
int phi[NMax];

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

    ll ans = 0;
    for (int j=2;j <= N;j += 2) {
        notPrime[j] = true;
        phi[j] -= phi[j]/2;
    }

    for (int i=3;i <= N;i += 2) {
        //ans += phi[i];

        if (notPrime[i]) {
            continue;
        }

        for (int j=i;j <= N;j += i) {
            notPrime[j] = true;
            phi[j] -= phi[j]/i;
        }
    }

    for (int i=2;i <= N;++i) {
        ans += phi[i];
        //cout<<phi[i]<<'\n';
    }

    out<<ans*2 + 1<<'\n';

    in.close();out.close();
    return 0;
}