FACE 2015 FREE GIFT

In this year of 2015, FACE is supporting the third edition of the Programming Marathon, but, at this time, organization's staff is requesting your help to create a lottery system by using the FACE letters. As this fair uses a differentiated and cheerful proposal, each participant who enters into the fair receives 4 letters, each of them in a different color and in the form of a wooden block, as shown in Figure 1, and they must insert them in a panel. If, by the entering time, the 4 letters create the opposite of the 4 last letters, this visitor will receive the free gift.

Figure 1 - FACE entrance on the panel followed by ACEF.

For example: suppose there have already been three visitors who entered into the fair and the letters' distribution remained as follows: F A C E E C F A A C F E A C E F. See that the panel, for being empty, the letters F A C E were inserted in order to start the process, now, as the fourth visitor enters, he has inserted the letters F E C A and, with it, they will receive the free gift as it got the opposite of A C E F. After this situation, the letters must remain F A C E E C F A A C F E. Another important fact is that, the free gifts' distribution occurs in a certain period with a sample of a selected visitors number. REMENBER, always when the panel remains empty it is automatically inserted the letters F A C E.