Statement

Edoardo was hacking a mainframe when he was traced by the cyberpolice (he didn't disconnect quickly enough). He is now in jail… but already planning his escape! In fact, Edoardo managed to get a hold on The Whip, an evil tool that his captors regularly use to punish prisoners. The rope is made by a handle and a set of N interconnected ropes which form a tree: at the root of this tree we find the whip's handle (numbered 0), and each rope i = 1 … N is directly tied to another rope P_i called parent rope (or to the handle if P_i = 0). Edoardo's plan is to untie some of the ropes (one by one) from their parent rope and then tie them back to some other rope on the whip in order to form a single, very long rope (the handle should remain on one end of the rope). This rope can then be used to get out of the jail...