#include <cstdio>
#include <iostream>

using namespace std;

int phi[1000010];

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

    int n;
    scanf("%d", &n);
    for(int i = 1; i <= n; i++)
        phi[i] = i - 1;
    for(int i = 1; i <= n; i++)
        for(int j = 2 * i; j <= n; j += i)
            phi[j] -= phi[i];
    long long ans = 1;
    for(int i = 1; i <= n; i++)
        ans = ans + 2LL * phi[i];
    cout << ans << '\n';
}