#include <iostream>
#include <queue>
#include <stack>
#include <map>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <set>
#include <algorithm>
#include <bitset>
#include <time.h>
#include <tuple>
#include <fstream>
#include <iomanip>
#include <utility>

#pragma warning "da 100% din tine. :)"
#define nl '\n'
#define sp ' '
#define pb(x) push_back(x)
#define all(v) v.begin(),v.end()
#define rall(v) v.rbegin(),v.rend()
#define SIZE 3000
#define NR 105
#define N 11
#define INF 10000

using namespace std;

int n;
unsigned long long s;
int v[1000001]; //phi(i) = v[i]

int main() {
    freopen("fractii.in", "r", stdin);
    freopen("fractii.out", "w", stdout);
    ios_base::sync_with_stdio(false);
//    clock_t tStart = clock();
    cin >> n;
    for (int i = 1; i <= n; ++i) {
        v[i] = i - 1; //toate s numere prime
        s += i - 1;
    }

    for (int i = 2; i <= n; ++i) {
        for (int j = (i << 1); j <= n; j += i) {
            v[j] -= v[i];
            s -= v[i];
        }
    }

    cout << s * 2 + 1;

//    printf("\nTime taken: %.2fs\n", (double) (clock() - tStart) / CLOCKS_PER_SEC);
}