create or replace function aa1(a1 integer[],a2 bigint) returns 
void AS $$
declare ii integer;
declare num integer;
  begin
  II:=1;
  num = 1;
  FOR ii IN 1..a2 LOOP 
  UPDATE student SET
    id=a1[num]
 WHERE cd_id = ii;
 num = num +1;
 if (num>6) then
  num = 1;
  end if;
  end loop;
  end;
$$ LANGUAGE plpgsql;

select aa1(array[1,4,5,6,7,8],6742)