#include <iostream>
#include <fstream>
using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
int n,a,b,r,phi[1000000];
int phix (int n){
int nr=0;
 for (int i = 1; i <= n; ++i)
    phi[i] = i-1;
for (int i = 2; i <=n ; ++i)
    for (int j = 2*i; j <= n; j += i)
        phi[j] -= phi[i];
for (int i=2;i<=n;i++)
  nr+=phi[i];
  nr=nr*2+1;
  return nr;
}
int main()
{
  f>>n;
  g<<phix(n);
  return 0;
}