from collections import deque

def main():
    twos = [1]
    for i in range(40):
        twos.append(twos[-1]*2)
    twos = set(twos)
    #print(twos)

    N = int(input()); INF = float("inf")
    N += 2
    start,end = map(int,input().split())
    stone = [start] + list(map(int,input().split())) + [end]
    G = [[] for _ in range(N)]
    for i in range(N):
        for j in range(i+1,N):
            k = stone[i]^stone[j]
            #print(i,j,k)
            if k in twos:
                G[i].append(j)
                G[j].append(i)
    #print(G)
    D = [-1]*N
    Q = deque([])
    Q.append(0)
    D[0] = 0
    while Q:
        v = Q.popleft()
        for u in G[v]:
            if D[u] != -1: continue
            D[u] = D[v] + 1
            Q.append(u)
    #print(D,N)
    if D[N-1] == -1:
        print(-1)
    else:
        print(D[N-1] - 1)

if __name__ == '__main__':
    main()