#include <fstream>
using namespace std;

const int kMaxN = 1000005;

int N, cnt[kMaxN];
int64_t ans = 1;

int main() {
    ifstream("fractii.in") >> N;
    for (int i = 2; i <= N; ++i)
        cnt[i] = i - 1;
    for (int i = 2; i <= N; ++i) {
        ans += 2 * cnt[i];
        for (int j = 2 * i; j <= N; j += i)
            cnt[j] -= cnt[i];
    }
    ofstream("fractii.out") << ans << "\n";
    return 0;
}