#include <iostream>
#include <fstream>
#define NM 1000002
using namespace std;

int n, phi[NM], mark[NM];
long long rez;

int main()
{
    ifstream fin ("fractii.in");
    ofstream fout ("fractii.out");
    fin >> n;
    for(int i = 2; i <= n; i++)
    {
        if(mark[i] == 0)
        {
            for(int j = 2; i * j <= n; j++)
            {
                phi[i * j] += j - 1;
                mark[i * j] = 1;
            }
        }
        rez += i - phi[i] - 1;
    }
    fout << rez * 2 + 1;
    return 0;
}