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 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 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 nextCharArray(){return myconv(next(), 0);} static ArrayList nextStrArray(int size){ ArrayList ret = new ArrayList<>(size); for(int i = 0; i < size; i++){ ret.add(next()); } return ret; } static ArrayList nextIntArray(int size){ ArrayList ret = new ArrayList<>(size); for(int i = 0; i < size; i++){ ret.add(Integer.parseInt(next())); } return ret; } static ArrayList nextLongArray(int size){ ArrayList 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 myconv(String str, int no){//only split String splitString = CONVSTR.get(no); return new ArrayList(Arrays.asList(str.split(splitString))); } static ArrayList myconv(String str, String no){ return new ArrayList(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; } HashSet list = new HashSet<>(nextIntArray(N)); list.add(S); list.add(T); HashMap access = new HashMap<>(); ArrayDeque queue = new ArrayDeque<>(); queue.add(S); access.put(S, 0); while(queue.size() > 0){ int now = queue.pollFirst(); int size = 31; for(int i = 0; i < size; i++){ int nx = now ^ (1 << i); if(list.contains(nx) && !access.containsKey(nx)){ queue.add(nx); access.put(nx, access.get(now) + 1); } } } if(access.containsKey(T)){ myout(access.get(T) - 1); }else{ myout(-1); } } //メソッド追加エリア ここから static class Node{ int V; ArrayList 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 }