from collections import deque
N = int(input())
A = [0]*(N+2)
a,b = map(int,input().split())
A[0] = a
A[N+1] = b
A[1:N+1] = map(int,input().split())
def dh(x,y):
    cnt = 0
    for k in range(30+1):
        if (x>>k)&1!=(y>>k)&1:
            cnt += 1
    return cnt
G = {i:[] for i in range(N+2)}
for i in range(N+1):
    for j in range(i+1,N+2):
        if dh(A[i],A[j])<=1:
            G[i].append(j)
            G[j].append(i)
dist = [-1]*(N+2)
dist[0] = 0
que = deque([0])
while que:
    x = que.popleft()
    for y in G[x]:
        if dist[y]==-1:
            dist[y] = dist[x]+1
            que.append(y)
if dist[N+1]<0:
    print(-1)
else:
    print(dist[N+1]-1)