program new;
{$I SRL/utils.simba}

procedure TStringArray.Scramble();
var i: Int32;
begin
  for i:=0 to High(self) do
    Swap(Self[i], Self[Random(Length(self))]);
end;

var
  doors: TStringArray = ['empty', 'empty', 'CAR'];
  available: TIntegerArray;
  i, w, empty, door: Int32;
begin
  doors.Scramble(); // randomize doors

  for i:=0 to 10000 do
  begin
    available := [0,1,2]; // the avilable doors

    // person: make a selection of 1 in 3 doors
    door := Random(3);

    // hostmaster removes a knowingly empty door that is also not equal
    // to your choice.
    empty := Random(3);
    while (empty = door) or (doors[empty] = 'CAR') do empty := Random(3);
    available.Remove(empty);

    //person: switch door!!
    if True then
    begin
      available.Remove(door); // se we remove the old selection
      door := available[0];   // only one door left now.
    end;

    // does it contain the car?
    if doors[door] = 'CAR' then
      inc(w);

    doors.Scramble(); // rescramble and repeat
  end;

  WriteLn(w / i);
end.