from collections import deque

n = int(input())
s, e = map(int, input().split())
stones = list(map(int, input().split()))
dic = {stone:i for i, stone in enumerate(stones, 2)}
dic[s] = 0
dic[e] = 1
dist = [-1] * (n + 2)
dist[0] = 0
queue = deque()
queue.append(s)

while queue:
    pos = queue.popleft()
    for i in range(30):
        npos = pos ^ (1 << i)
        if npos not in dic:
            continue
        p = dic[npos]
        if dist[p] != -1:
            continue
        dist[p] = dist[dic[pos]] + 1
        queue.append(npos)
if dist[1] == -1:
    print(-1)
else:
    print(dist[1] - 1)