#include <bits/stdc++.h>
#define ll long long
#define INF 0x3F3F3F3F
using namespace std;

const string file = "fractii";

ifstream fin (file + ".in");
ofstream fout (file + ".out");

const int N_MAX = 1e6 + 1;

ll N ,rezult;
bool upd[N_MAX];

int main()
{
    fin>>N; fin.close(); rezult = N;

    for(int i=2; i<=N; i++)
    {
        if(!upd[i])
        {
            int vcmb = N - 1;

            int found = 1;

            for(int j=2; j*i<=N; j++)
            {
                vcmb -= 2*found; found++;
                upd[j*i] = true;
            }

            rezult+=vcmb;
        }
        else
        {
            rezult+=N - 1;
        }
    }

    fout<<rezult; fout.close(); //cout<<rezult;
}