CF242D Dispute

Valera has $ n $ counters numbered from $ 1 $ to $ n $ . Some of them are connected by wires, and each of the counters has a special button. Initially, all the counters contain number $ 0 $ . When you press a button on a certain counter, the value it has increases by one. Also, the values recorded in all the counters, directly connected to it by a wire, increase by one. Valera and Ignat started having a dispute, the dispute is as follows. Ignat thought of a sequence of $ n $ integers $ a_{1},a_{2},...,a_{n} $ . Valera should choose some set of distinct counters and press buttons on each of them exactly once (on other counters the buttons won't be pressed). If after that there is a counter with the number $ i $ , which has value $ a_{i} $ , then Valera loses the dispute, otherwise he wins the dispute. Help Valera to determine on which counters he needs to press a button to win the dispute.

N/A

N/A