with Ada.Text_IO; use Ada.Text_IO;

procedure P is

    type Operation_Mode is
      (NonInitializeMode,
       AutomaticMode,
       SetupMode,
       SelectOnlyMode,
       ServiceModeLet,
       ResetMode);

    ModOpn : Operation_Mode := NonInitializeMode;

begin
    loop
       if ModOpn = Operation_Mode'Last then
          ModOpn := Operation_Mode'First;
       else
          ModOpn := Operation_Mode'Succ (ModOpn);
       end if;
       Put_Line (ModOpn'Img);  -- LINE 22 is here
     end loop;
end P;