n,S,G,*a, = map(int,open(0).read().split())
n += 2
a += [S,G]
g = [[] for _ in range(n)]
for i in range(n):
    for j in range(n):
        v = a[i]^a[j]
        if v and v&(v-1)==0:
            g[i].append(j)

d = [-1]*n
q = [n-2]
d[n-2] = 0
for v in q:
    for i in g[v]:
        if d[i] == -1:
            d[i] = d[v] + 1
            q.append(i)
print(max(-1,d[-1]-1))