var mapStone: dict<int, bool>
var mapNext: dict<int, bool>
var e: int

func main()
	var n: int :: cui@inputInt()
	var s: int :: cui@inputInt()
	var e: int :: cui@inputInt()
	
	do @mapStone :: #dict<int, bool>
	do @mapStone.add(e, true)
	for(1, n)
		var stone: int :: cui@inputInt()
		do @mapStone.add(stone, true)
	end for
	do @mapNext :: #dict<int, bool>
	do @mapNext.add(s, true)
	
	var ans: int :: 0
	while(^@mapNext <> 0 & ans <> 5)
		do ans :+ 1
		var mapCurrent: dict<int, bool> :: ##@mapNext
		do @mapNext :: #dict<int, bool>
		do mapCurrent.forEach(callback, null)
		if(@mapNext.get(e, &))
			do cui@print("\{ans - 1}\n")
			ret
		end if
	end while
	
	do cui@print("-1\n")
	
	func callback(key: int, value: bool, data: kuin@Class): bool
		for i(0, 30)
			var v: int :: (key $ bit32).xor((2 ^ i) $ bit32) $ int
			;do cui@print("\{key} \{v}\n")
			if(@mapStone.get(v, &))
				do @mapNext.add(v, true)
			end if
		end for
		ret true
	end func
end func