from collections import deque


def bfs(G, s, N):
    Q = deque([])
    dist = [-1] * N
    par = [-1] * N
    dist[s] = 0
    for u in G[s]:
        par[u] = s
        dist[u] = 1
        Q.append(u)

    while Q:
        u = Q.popleft()
        for v in G[u]:
            if dist[v] != -1:
                continue
            dist[v] = dist[u] + 1
            par[v] = u
            Q.append(v)
            
    return dist

N = int(input())
s, g = map(int, input().split())
X = [s] + list(map(int, input().split())) + [g]
D = dict()
N += 2
for i in range(N):
    D[X[i]] = i
    
G = [[] for i in range(N)]
for i in range(N):
    for j in range(35):
        now = X[i] ^ (1 << j)
        if now in D:
            u = D[now]
            G[i].append(u)

DD = bfs(G, 0, N)
print(DD[-1] - 1) if DD[-1] != -1 else print(-1)