// Example program
#include <iostream>
#include <fstream>
#include <string>
#include <math.h>
using namespace std;

int noOfPrimeWith(int n) {
    int result = 1;
    int m = n;
    for (int i = 2; i <= m/2; i++) {
        if (n % i == 0) {
            int alpha = 0;
            while (n % i == 0) {
                alpha++;
                n /= i;
            }
            result *= pow(i, alpha - 1) * (i - 1);
        }
    }
    if (result == 1) {
        return m - 1;
    }
    return result;
}

int main()
{
    int n, sum = 1;
    ifstream f("fractii.in");
    ofstream g("fractii.out");
    f >> n;
    for (int i = 2; i <= n; i++) {
        sum += 2 * noOfPrimeWith(i);
    }
    g << sum;
}