The game.
We have 3 rooms. On each prob a bonus is placed in one room, two others remain empty. We choose a room. Then one of the remaining rooms, which is empty, is open to show there is no bonus in it. Now we have the right to leave our first choice or change it, and choose another closed yet room. The chosen room is open and we see if we win the bonus or lose.

The program has options:

• -n defines the number of probs (default is 100);
• -change applies the right to change the chosen room;
• -nochange do not use the right to change the chosen room (default).

It outputs the percentage of wins.