Declare 
   a integer :=&a;
   i integer;
   
begin
  for i in 1 .. a
   loop
      if (mod(i,2)=0) then
         dbms_output.put_line('even '||i);
     -- else
     -- dbms_output.put_line('odd '||i);
    end if;
  end loop;
end;
/