#include <bits/stdc++.h>
using ll = long long;
#define rep(i, n) for (int i = 0, i##_len = (n); i < i##_len; ++i)
#define rrep(i, n) for (int i = ((int)(n)-1); i >= 0; --i)
#define all(v) begin(v), end(v)
using namespace std;

vector<int> min_pf;

void prime_factorize_init(int n) {
    min_pf.resize(n + 1, 0);
    for (int i = 2; i <= n; i++) {
        if (min_pf.at(i) == 0) {
            for (int mul = i; mul <= n; mul += i) {
                min_pf.at(mul) = i;
            }
        }
    }
}

vector<int> prime_factorize(int n) {
    vector<int> res;
    if (n <= 1) return res;
    while (n != 1) {
        res.push_back(min_pf.at(n));
        n /= min_pf.at(n);
    }
    res.erase(unique(res.begin(), res.end()), res.end());
    return res;
}

constexpr int N = 1000'000;
int main() {
    prime_factorize_init(N);

    int n;
    cin >> n;

    vector<int> cnt(N + 1);

    ll ans = ll(n) * (n - 1) / 2 - (n - 1);
    for (int i = n; i > 1; --i) {
        ans -= (n / i) - 1;

        auto pf = prime_factorize(i);
        ll x = 0;
        for (int S = 0; S < (1 << pf.size()); ++S) {
            int mul = 1;
            for (int i = 0; i < pf.size(); ++i)
                if (S >> i & 1) mul *= pf[i];

            if (__builtin_parity(S)) x -= cnt[mul];
            else x += cnt[mul];
            cnt[mul]++;
        }
        ans -= x;
    }

    cout << ans << endl;
}