#include <cstdlib>
#include <fstream>
#include <iostream>
#include <algorithm>
#include <math.h>
#include <map>
#include <set>
#include <bitset>
#include <vector>

using namespace std;

void doPrimes(int v[], const int n) {
    int pos=0;
    bitset < 1000001 > bs;
    for (int i = 2; i <= n; i++) {
        if (!bs[i]) {
            bs[i] = true;
            int j = 2 * i;
            while (j < n + 1) {
                bs[j] = true;
                j += i;
            }
            v[pos]=i;
            pos++;
//                        cout << i << " ";
        }
    }
}

long long totient(int p[], int n) {
    long long t = 1;
    for (unsigned int i = 0; i < 100000; i++) {
        if(p[i] > n || p[i]==0) break;
        bool has = false;
        while (n % p[i] == 0) {
            n /= p[i];
            if (!has) {
                has = true;
                t *= p[i] - 1;
                continue;
            }
            t *= p[i];
        }
    }
    return t*n;
}

int main() {

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

    int n;
    in >> n;

    int v[100000];
    doPrimes(v, n);
    long long t = 1;
    for (int i = 2; i <= n; i++) {
        //            for (int i = 2; i <= 10; i++) {
        long long tot = totient(v, i);
        t += tot * 2;
        //                        cout << i << "->" << tot << " ," << t << endl;
    }

    cout << t;
    out << t;

    return 0;
}