var n,nr,phi,r:int64;
    i,j:longint;
    f,g:text;
begin
 assign(f,'fractii.in'); reset(f);
 assign(g,'fractii.out'); rewrite(g);
 read(f,n);
 r:=1;
 for i:=2 to n do begin
  nr:=i;
  phi:=nr;
  for j:=2 to trunc(sqrt(i)) do begin
   if nr mod j=0 then
    phi:=(phi*(j-1)) div j;
   while nr mod j=0 do
    nr:=nr div j;
  end;
  if nr>1 then
   phi:=(phi*(nr-1)) div nr;
  r:=r+2*phi;
 end;
 writeln(g,r);
 closE(f); close(g);
end.