package main

import . "fmt"
import . "math/bits"

func main() {
	var n, start,end int
	Scan(&n,&start,&end)
	stone := make([]int, n)
	for i := range stone {
		Scan(&stone[i])
	}
	current := []int{start}
	visited := make(map[int]bool)
	visited[start] = true
	cnt := 0
	for len(current) > 0 {
		tmp := []int{}
		for _, v := range current {
			if OnesCount(uint(v^end)) == 1 {
				Println(cnt)
				return
			}
			for _, s := range stone {
				if visited[s] {
					continue
				}
				if OnesCount(uint(v^s)) == 1 {
					visited[s] = true
					tmp = append(tmp, s)
				}
			}
		}
		current = tmp
		cnt++
	}
	Println(-1)
}

/*
考察

石を頂点、ハミング距離1を辺としてグラフ作って
頂点startから頂点endまでの最短ルートの端点以外の頂点数が答え
*/