import java.util.*; import java.io.*; import java.math.*;
public class Main{
	//見なくていいよ　ここから------------------------------------------
	static class InputIterator{
		ArrayList<String> inputLine = new ArrayList<>(1024);
		int index = 0; int max; String read;
		InputIterator(){
			try{
				BufferedReader br = new BufferedReader(new InputStreamReader(System.in, "UTF-8"));
				while((read = br.readLine()) != null){
					inputLine.addAll(Arrays.asList(read.split(" ")));
				}
			}catch(IOException e){}
			max = inputLine.size();
		}
		boolean hasNext(){return (index < max);}
		String next(){
			if(hasNext()){
				return inputLine.get(index++);
			}else{
				throw new IndexOutOfBoundsException("There is no more input");
			}
		}
	}
	static HashMap<Integer, String> CONVSTR = new HashMap<>();
	static InputIterator ii = new InputIterator();//This class cannot be used in reactive problem.
	static PrintWriter out = new PrintWriter(System.out);
	static void flush(){out.flush();}
	static void myout(Object t){out.println(t);}
	static void myerr(Object... t){System.err.print("debug:");System.err.println(Arrays.deepToString(t));}
	static String next(){return ii.next();}
	static boolean hasNext(){return ii.hasNext();}
	static int nextInt(){return Integer.parseInt(next());}
	static long nextLong(){return Long.parseLong(next());}
	static double nextDouble(){return Double.parseDouble(next());}
	static ArrayList<String> nextCharArray(){return myconv(next(), 0);}
	static ArrayList<String> nextStrArray(int size){
		ArrayList<String> ret = new ArrayList<>(size);
		for(int i = 0; i < size; i++){
			ret.add(next());
		}
		return ret;
	}
	static ArrayList<Integer> nextIntArray(int size){
		ArrayList<Integer> ret = new ArrayList<>(size);
		for(int i = 0; i < size; i++){
			ret.add(Integer.parseInt(next()));
		}
		return ret;
	}
	static ArrayList<Long> nextLongArray(int size){
		ArrayList<Long> ret = new ArrayList<>(size);
		for(int i = 0; i < size; i++){
			ret.add(Long.parseLong(next()));
		}
		return ret;
	}
	@SuppressWarnings("unchecked")
	static String myconv(Object list, int no){//only join
		StringBuilder sb = new StringBuilder("");
		String joinString = CONVSTR.get(no);
		if(list instanceof String[]){
			return String.join(joinString, (String[])list);
		}else if(list instanceof long[]){
			long[] tmp = (long[])list;
			if(tmp.length == 0){
				return "";
			}
			sb.append(String.valueOf(tmp[0]));
			for(int i = 1; i < tmp.length; i++){
				sb.append(joinString).append(String.valueOf(tmp[i]));
			}
			return sb.toString();
		}else if(list instanceof int[]){
			int[] tmp = (int[])list;
			if(tmp.length == 0){
				return "";
			}
			sb.append(String.valueOf(tmp[0]));
			for(int i = 1; i < tmp.length; i++){
				sb.append(joinString).append(String.valueOf(tmp[i]));
			}
			return sb.toString();
		}else if(list instanceof ArrayList){
			ArrayList tmp = (ArrayList)list;
			if(tmp.size() == 0){
				return "";
			}
			sb.append(tmp.get(0));
			for(int i = 1; i < tmp.size(); i++){
				sb.append(joinString).append(tmp.get(i));
			}
			return sb.toString();
		}else{
			throw new ClassCastException("Don't join");
		}
	}
	static ArrayList<String> myconv(String str, int no){//only split
		String splitString = CONVSTR.get(no);
		return new ArrayList<String>(Arrays.asList(str.split(splitString)));
	}
	static ArrayList<String> myconv(String str, String no){
		return new ArrayList<String>(Arrays.asList(str.split(no)));
	}
	public static void main(String[] args){
		CONVSTR.put(8, " "); CONVSTR.put(9, "\n"); CONVSTR.put(0, "");
		solve();flush();
	}
	//見なくていいよ　ここまで------------------------------------------
	//このコードをコンパイルするときは、「-encoding UTF-8」を指定すること
	static void solve(){//ここがメイン関数
		int N = nextInt();
		int S = nextInt();
		int T = nextInt();

		int tmpL = S;
		int tmpR = T;
		int tmpC = 0;
		while(tmpL > 0 || tmpR > 0){
			if(tmpL % 2 != tmpR % 2){
				tmpC++;
			}
			tmpL /= 2;
			tmpR /= 2;
		}
		if(tmpC <= 1){
			myout(0);
			return;
		}
		Node[] list = new Node[N + 2];
		for(int i = 0; i < N; i++){
			list[i] = new Node(nextInt());
		}
		list[N] = new Node(S);
		list[N + 1] = new Node(T);
		for(int i = 0; i < N + 2; i++){
			for(int j = i + 1; j < N + 2; j++){
				int L = list[i].V;
				int R = list[j].V;
				int C = 0;
				while(L > 0 || R > 0){
					if(L % 2 != R % 2){
						C++;
					}
					L /= 2;
					R /= 2;
				}
				if(C <= 1){
					list[i].child.add(j);
					list[j].child.add(i);
				}
			}
		}

		ArrayDeque<Integer> queue = new ArrayDeque<>();
		queue.add(N);
		list[N].access = 0;
		while(queue.size() > 0){
			int now = queue.pollFirst();
			Node node = list[now];
			ArrayList<Integer> child = node.child;
			for(int nx : child){
				if(list[nx].access == -1){
					list[nx].access = list[now].access + 1;
					queue.add(nx);
				}
			}
		}
		myout(Math.max(list[N + 1].access - 1, -1));
	}
	//メソッド追加エリア　ここから

static class Node{
	int V;
	ArrayList<Integer> child = new ArrayList<>();
	int access = -1;
	Node(int V){
		this.V = V;
	}
	public String toString(){
		return child.toString();
	}
}

	//メソッド追加エリア　ここまで
}