CF285B Find Marble

Petya and Vasya are playing a game. Petya's got $ n $ non-transparent glasses, standing in a row. The glasses' positions are indexed with integers from $ 1 $ to $ n $ from left to right. Note that the positions are indexed but the glasses are not. First Petya puts a marble under the glass in position $ s $ . Then he performs some (possibly zero) shuffling operations. One shuffling operation means moving the glass from the first position to position $ p_{1} $ , the glass from the second position to position $ p_{2} $ and so on. That is, a glass goes from position $ i $ to position $ p_{i} $ . Consider all glasses are moving simultaneously during one shuffling operation. When the glasses are shuffled, the marble doesn't travel from one glass to another: it moves together with the glass it was initially been put in. After all shuffling operations Petya shows Vasya that the ball has moved to position $ t $ . Vasya's task is to say what minimum number of shuffling operations Petya has performed or determine that Petya has made a mistake and the marble could not have got from position $ s $ to position $ t $ .

The first line contains three integers: $ n,s,t\ (1

If the marble can move from position $ s $ to position $ t $ , then print on a single line a non-negative integer — the minimum number of shuffling operations, needed to get the marble to position $ t $ . If it is impossible, print number -1.