#include <fstream>

#define maxn 1000010
using namespace std;

long long phi[maxn];
int n;

void calculatePhi() {
    for (int i = 1; i <= n; i++)
        phi[i] = i - 1;

    for (int i = 2; i <= n; i++)
        for (long long j = 2LL * i; j <= n; j += i)
            phi[j] -= phi[i];
}

int main() {
    ifstream in("fractii.in");
    ofstream out("fractii.out");

    in >> n;
    calculatePhi();

    long long result = 1;
    for (int i = 1; i <= n; i++)
        result += 2LL * phi[i];

    out << result;
    return 0;
}