#include <cassert>
#include <cstdio>

const int MAX_N = 1000005;

int n;
int v[MAX_N];

int main() {
    assert(freopen("fractii.in", "r", stdin));
    assert(freopen("fractii.out", "w", stdout));

    assert(scanf("%d", &n) == 1);

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

    long long ans = 1;
    for (int i = 2; i <= n; ++i)
        ans += 2 * v[i];
    printf("%lld\n", ans);
}