#include <bits/stdc++.h>
#define int long long

using namespace std;

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

int n,nr;

const int MAX=1e6;

int phi[MAX+5],t,x,rez;

void euler()
{
   for (int i=0; i<=MAX; i++)
      phi[i]=i;

   for (int i=2; i<=MAX; i++ )
      if ( phi[i]==i )
         for (int j=i; j<=MAX; j+=i )
            phi[j]=phi[j]/i*(i-1);
}

signed main()
{
    f >> n;
    euler();
    for (int i=1; i<=n; i++ )
        rez+=phi[i];
    rez*=2;
    g << rez-1;
    return 0;
}