program fractii;
 var phi:array[1..1000000] of longint;
     n,i,j,ans:longint;
 begin
  assign(input,'fractii.in');
  assign(output,'fractii.out');
  reset(input);
  rewrite(Output);
  readln(n);
  for i:=1 to n do phi[i]:=i-1;
  for i:=2 to n do
   begin
    j:=i*2;
    while j<=n do begin
      phi[j]:=phi[j]-phi[i];
      j:=j+i;
         end;
    end;
   for i:=2 to n do ans:=ans+2*phi[i];
   inc(ans);
   write(ans);
   close(output);
  end.