function min(a, b: integer): integer;
begin
  min := a;
  if b < a then min := b;
end;

const
  size_answered = 9;
var
  stud: char;
  quest: set of byte;
  students: set of char;
  i, stud_number, current: byte;

  answered: array[1 .. size_answered] of byte;

begin
  quest := [1 .. 15];
  students := ['A' .. 'Z'];
  for stud_number := 1 to 26 do begin

    repeat
      stud := chr(ord('A') + random(26));
    until stud in students;
    exclude(students, stud);

    if stud_number > size_answered then begin

      writeln('adding the first answered question...');
      include(quest, answered[1]);

      for i := 1 to pred(size_answered) do
        answered[i] := answered[succ(i)];

    end;
    write('student: ', stud, ' is entering the class...');

    repeat
      current := random(15) + 1;
    until current in quest;

    writeln(' ... and getting quest #', current);
    exclude(quest, current);

    answered[min(size_answered, stud_number)] := current;

  end;
end.