#include <iostream>
#include <fstream>
using namespace std;

int n, sir[1000005], rez;

ifstream f("fractii.in");
ofstream g("fractii.out");

void solve()
{
    for (int i=2; i<=n; ++i)
    {
        rez+=2*sir[i];
        for (int j=2*i; j<=n; j+=i)
        {
            sir[j]-=sir[i];
        }
    }
    g << rez+1;
}

int main()
{
    f >> n;
    for (int i=2; i<=n; ++i)
    {
        sir[i]=i-1;
    }
    solve();
    return 0;
}