#include <bits/stdc++.h>
#define nmax 1000005
using namespace std;

int fi[nmax], n;

void Phi()
{
    int i, j;
    for(i = 1; i <= 1000000; i++)
        fi[i] = i - 1;
    for(i = 2; i <= 1000000; i++)
        for(j = i + i; j <= 1000000; j += i)
            fi[j] -= fi[i];
}

void Citire()
{
    ifstream fin("fractii.in");
    fin >> n;
    fin.close();
}

void Afisare()
{
    int i;
    long long cnt = 0;
    for (i = 2; i <= n; ++i)
        cnt += fi[i];
    cnt *= 2;
    cnt++;
    ofstream fout("fractii.out");
    fout << cnt << "\n";
    fout.close();
}

int main()
{
    Citire();
    Phi();
    Afisare();
    return 0;
}