from collections import deque

n = int(input())
start, end = map(int, input().split())
stones = list(map(int, input().split()))

# Create a list of all nodes including start, stones, and end
nodes = [start] + stones + [end]
total_nodes = len(nodes)
end_idx = total_nodes - 1  # Index of the end node

distance = [-1] * total_nodes
distance[0] = 0  # Start node is at index 0

q = deque([0])

found = False
while q:
    current = q.popleft()
    
    # Check if current node is the end node
    if current == end_idx:
        found = True
        break
    
    current_val = nodes[current]
    for other_idx in range(total_nodes):
        if other_idx == current:
            continue
        other_val = nodes[other_idx]
        # Calculate Hamming distance
        xor = current_val ^ other_val
        ham = bin(xor).count('1')
        if ham <= 1 and distance[other_idx] == -1:
            distance[other_idx] = distance[current] + 1
            q.append(other_idx)
            if other_idx == end_idx:
                found = True
                # Early exit if end is found
                q = deque()
                break

if distance[end_idx] == -1:
    print(-1)
else:
    print(max(0, distance[end_idx] - 1))