var f,g:Text;
    n:longint;
    v:array[1..1000000] of longint;
    i,j:longint;
    nr:qword;

begin
 assign (f,'fractii.in'); reset (f);
 assign (g,'fractii.out'); rewrite (g);
 read (f,n);
 for i:=1 to n do
  v[i]:=i;
 nr:=2;
 for i:=2 to n do
 begin
  if v[i]=i then
  begin
   j:=i;
   while j<=n do
   begin
    v[j]:=v[j] div i;
    v[j]:=v[j]*(i-1);
    j:=j+i;
   end;
  end;
   nr:=nr+2*v[i];
 end;
 write (g,nr-1);
 close (F); close (g);
end.