begin
  for SELECT max(person.lschet) FROM person
  into :max_person
  do nothing=0;

  for SELECT max(person_arhiv.lschet) FROM person_arhiv
  into :max_arhiv
  do nothing=0;

  if (max_arhiv<=max_person) then
   max_person_id=max_person;
  else max_person_id=max_arhiv;

  i=1;
  while (i<=:max_person_id) do
   begin
    lschet1=-1;
    lschet2=-1;
    for select person.lschet
    from person
    where (person.lschet) = :i
    into :lschet1
    do nothing=0;
    if (lschet1=-1) then
     begin
      for select person_arhiv.lschet
      from person_arhiv
      where (person_arhiv.lschet) = :i
      into :lschet2
      do nothing=0;
     end
    if ((:lschet1 =-1)and(:lschet2=-1)) then
     begin
      lschet_new:=:i; 
      exit;
    end
    i=:i+1;
   end
end

select max(person.lschet)
from person
where person.lschet < max_person_id