#include <fstream>
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
int euler[1000007];

int main() {
    int n, i, j;
    long long s = 1;
    f >> n;
    euler[1] = 1;
    for (i = 2; i < 1000007; ++i)
        euler[i] = i - 1;
    for (i = 2; i < 1000007; ++i)
        for (j = i * 2; j < 1000007; j += i)
            euler[j] -= euler[i];
    for(i = 2; i <= n; i++)
        s += 2 * euler[i];
    g << s;


    f.close();
    g.close();
    return 0;
}