#include <iostream>
#include <fstream>
#include <vector>
using namespace std;
 
int numere[1000005];
 
ifstream fin("fractii.in");
ofstream fout("fractii.out");
 
long long ciurulluieratostene(int n)
{
    int i,j;
    for (i = 2; i <= n; i++)
    {
        numere[i] = i - 1;
    }
    for (i = 2; i <= n; i++)
    {
        for (j = 2 * i; j <= n; j+=i)
        {
            numere[j] -= numere[i];
        }
    }
    long long total=0;
    for (i = 1; i <= n; i++)total += numere[i];
    total *= 2;
    total++;
    return total;
}
 
int main()
{
    int i,j,curent;
    int n;
    fin >> n;
    fout << ciurulluieratostene(n);
}