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 .

输入描述:

The first line contains three integers: n, s, t (1 ≤ n ≤ 105; 1 ≤ s, t ≤ n) — the number of glasses, the ball's initial and final position. The second line contains n space-separated integers: p1, p2, ..., pn (1 ≤ pi ≤ n) — the shuffling operation parameters. It is guaranteed that all pi's are distinct.Note that s can equal t.

输出描述:

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.