There is an array with n elements a1, a2, ..., an and the number x.

In one operation you can select some i (1 ≤ i ≤ n) and replace element ai with ai & x, where & denotes the [bitwise and](https://en.wikipedia.org/wiki/Bitwise_operation#AND) operation.

You want the array to have at least two equal elements after applying some operations (possibly, none). In other words, there should be at least two distinct indices i ≠ j such that ai = aj. Determine whether it is possible to achieve and, if possible, the minimal number of operations to apply.

Input

The first line contains integers n and x (2 ≤ n ≤ 100 000, 1 ≤ x ≤ 100 000), number of elements in the array and the number to and with.

The second line contains n integers ai (1 ≤ ai ≤ 100 000), the elements of the array.

Output

Print a single integer denoting the minimal number of operations to do, or -1, if it is impossible.

Examples

Input

4 3
1 2 3 7


Output

1


Input

2 228
1 1


Output

0


Input

3 7
1 2 3


Output

-1

Note

In the first example one can apply the operation to the last element of the array. That replaces 7 with 3, so we achieve the goal in one move.

In the second example the array already has two equal elements.

In the third example applying the operation won't change the array at all, so it is impossible to make some pair of elements equal.
			     
			import java.io.*;
			        		    import java.math.*;
			        		    import java.util.*;
		import java.util.regex.Pattern;
		
			    	     
			        		    public class Main{
			        		  	private static InputStream stream;
			        		    	private static byte[] buf = new byte[1024];
			        		    	private static int curChar;
			        		    	private static int numChars;
			        		    	private static SpaceCharFilter filter;
			        		    	private static PrintWriter pw;
			        		    	private static long count = 0,mod=(long)1e9+7;
			        		    //	private static TreeSet<Integer> ts=new TreeSet[200000];
			public final static int INF = (int) 1E9;
			
			public static void main(String args[]) {
		    	
				InputReader(System.in);
				pw = new PrintWriter(System.out); 
			    new Thread(null ,new Runnable(){
			       public void run(){
			           try{
			        		
			               test();
		
			               pw.close();
			           } catch(Exception e){
			               e.printStackTrace();
			           }
			       }
			   },"1",1<<26).start();
			   	   }
			    static StringBuilder sb;
			    public static void test() throws IOException{
			    	 sb=new StringBuilder();
			    	
			    	 int t=1;
			    	 
			    	 while(t-->0){
			    		
			    		solve();
			    		//pw.println();
			    		//sb.append("\n");
			    	}
			    	//pw.println(sb);
			    }
			    
			    public static long pow(long n, long p,long mod) {
					if(p==0)
						return 1;
					if(p==1)
						return n%mod;
					if(p%2==0){
						long temp=pow(n, p/2,mod);
					return (temp*temp)%mod;
					}else{
						 	long temp=pow(n,p/2,mod);
						 	temp=(temp*temp)%mod;
						 	return(temp*n)%mod;
						 	
					}
				}
			    public static long pow(long n, long p) {
					if(p==0)
						return 1;
					if(p==1)
						return n;
					if(p%2==0){
						long temp=pow(n, p/2);
					return (temp*temp);
					}else{
						 	long temp=pow(n,p/2);
						 	temp=(temp*temp);
						 	return(temp*n);
						 	
					}
				}
			    public static void Merge(long a[],int p,int r){
			        if(p<r){
			            int q = (p+r)/2;
			            Merge(a,p,q);
			            Merge(a,q+1,r);
			            Merge_Array(a,p,q,r);
			        }
			    }
			    public static void Merge_Array(long a[],int p,int q,int r){
			       long b[] = new long[q-p+1];
			        long c[] = new long[r-q];
			        for(int i=0;i<b.length;i++)
			            b[i] = a[p+i];
			        for(int i=0;i<c.length;i++)
			            c[i] = a[q+i+1];
			        int i = 0,j = 0;
			        for(int k=p;k<=r;k++){
			            if(i==b.length){
			                a[k] = c[j];
			                j++;
			            }
			            else if(j==c.length){
			                a[k] = b[i];
			                i++;
			            }
			            else if(b[i]<c[j]){
			                a[k] = b[i];
			                i++;
			            }
			            else{
			                a[k] = c[j];
			                j++;
			            }
			        }
			    }
			    
			  
				public static long gcd(long x, long y) {
					if (x == 0)
						return y;
					else
						return gcd( y % x,x);
				}	
				
				public static boolean isPrime(int n) {
					if (n <= 1)
						return false;
					if (n <= 3)
						return true;
			 
					if (n % 2 == 0 || n % 3 == 0)
						return false;
			 
					for (int i = 5; i * i <= n; i = i + 6)
						if (n % i == 0 || n % (i + 2) == 0)
							return false;
			 
					return true;
				}
				
			        static LinkedList<Integer> adj[],adj2[];
			        static boolean Visited[];
			        static HashSet<Integer> exc;
			        static long oddsum[]=new long[1000001];
			        static long co=0;
			        static int indeg[],outdeg[];
	  		      
			    
			    	private static void buildgraph(int n){
			    		adj=new LinkedList[n+1];
			    		adj2=new LinkedList[n+1];
			    		Visited=new boolean[n+1];
			    		levl=new int[n+1];
			    		indeg=new int[n+1];
			    		outdeg=new int[n+1];
			    		for(int i=0;i<=n;i++){
			    			adj[i]=new LinkedList<Integer>();
			    			adj2[i]=new LinkedList<Integer>();
			    		}
			
			
			    	}
			      
			       
			        static int[] levl;
			        static int[] eat;
			        static int n,m;
			        static int price[];
			        //ind frog crab
			    
			        
			        static long d,x,y;
					static long modInverse(long A, long M)
					{
					extendedEuclid(A,M);
					return (x%M+M)%M;    //x may be negative
					}
					static void extendedEuclid(long A, long B) {
					if(B == 0) {
					d = A;
					x = 1;
					y = 0;
					}
					else {
					extendedEuclid(B, A%B);
					long temp = x;
					x = y;
					y = temp - (A/B)*y;
					}
					}
			        static double distance(int x1,int y1,int x2,int y2){
			        	return Math.sqrt((x1-x2)*(x1-x2) + (y1-y2)*(y1-y2));
			        }
			        static double area(int x1, int y1, int x2, int y2, int x3, int y3)
			        {
			           return Math.abs((x1*(y2-y3) + x2*(y3-y1)+ x3*(y1-y2))/2.0);
			        }
			        static boolean isInside(int x1, int y1, int x2, int y2, int x3, int y3, int x, int y)
			        {   
			           double A = area (x1, y1, x2, y2, x3, y3);
			         
			           double A1 = area (x, y, x2, y2, x3, y3);
			         
			           double A2 = area (x1, y1, x, y, x3, y3);
			         
			           double A3 = area (x1, y1, x2, y2, x, y);
			           
			          return (A == A1 + A2 + A3);
			        }
			      
					static int col[];
			    public static boolean isVowel(char c){
			    	if(c=='a' || c=='e'||c=='i' || c=='o' || c=='u')
			    		return true;
			    	return false;
			    }
			static long arr[], lazy[],ans[];
			static int c[],nodes[];
			static int dp[][];
			static long a[][];
			
			private static boolean isPrim(long n,int p){
				for (long i = 2; i * i <= n; i++) {
			        if (n % i == 0 && i <= p) return false;
			    }
			    return true;
			}
			//price - starting index of string with given hash
			//rating-count of number of time of a hash
			static ArrayList<String> all_perm;
			static boolean[][] visited1;
			static  boolean won;
			static boolean containsCycle;
			static ArrayList<Integer> anss;
			static int index = 0;
			static int trav[],subtree[];
		public static void solve() throws IOException{
				int n=nextInt();
				long x=nextLong();
				long a[]=nextLongArray(n);
			HashMap<Long,Integer> hm = new HashMap<Long, Integer>();
			HashMap<Long,Integer> hmand = new HashMap<Long, Integer>();
			
			for(int i=0;i<n;i++){
				if(!hm.containsKey(a[i])){
					hm.put(a[i], 1);
				}else{
					hm.replace(a[i], hm.get(a[i])+1);
				}
			}
			for(int i=0;i<n;i++){
				if(!hmand.containsKey(a[i]&x)){
					hmand.put(a[i]&x, 1);
				}else{
					hmand.replace(a[i]&x, hmand.get(a[i]&x)+1);
				}
			}
			int min=Integer.MAX_VALUE;
			for(int i=0;i<n;i++){
				if(hm.get(a[i])>1){
					min=Math.min(min, 0);
				}
				if(hmand.containsKey(a[i])){
					if(a[i]==(a[i]&x)){
						if(hmand.get(a[i])>1){

							min=Math.min(min,1);		
						}
					}else{
						if(hmand.get(a[i])>=1){

							min=Math.min(min,1);
						}
					}
					
				}
				if(hmand.get(a[i]&x)>1){
					min=Math.min(2, min);
				}
			}
			if(min==Integer.MAX_VALUE)
				min=-1;
			pw.println(min);
				
		}
		static int res=0;
		private static void dfs(int start, int par){
			Visited[start] = true;
			trav[index] = start;
			index++;
			for(int x: adj[start]){
				if(!Visited[x]){
					dfs(x, start);
				}
			}
			subtree[start]++;
			subtree[par]+=subtree[start];
		}
		
					private static boolean check(int x,int y,int n,int m){
				if(x>=0 && x<n && y>=0 && y<m)
					return true;
				return false;
			}
					
					
					
								
			
			    private static boolean Check(int x,int y,int n){
					if(x>=0 && x<n && y>=0 && y<n)
						return true;
					return false;
				}
			    
			    public static String reverseString(String s) {
					StringBuilder sb = new StringBuilder(s);
					sb.reverse();
					return (sb.toString());
				}
			    
			  /*  
			   private static void BFS(int sou){
			    	Queue<Integer> q=new LinkedList<Integer>();
			    	q.add(sou);
			    	Visited[sou]=true;
			    	levl[sou]=0;
			    	while(!q.isEmpty()){
			    		int top=q.poll();
			    		
			    		for(int i:adj[top]){
			    			//pw.println(i+" "+top);
						if(!Visited[i])
						{
							
							q.add(i);
							levl[i]=levl[top]+1;
						}
						
						Visited[i]=true;
						
						}
					}
				}*/
				
			
			
			
			    		      
			    		   /* private static void kahn(int n){
			    		    	
			    		    	PriorityQueue<Integer> q=new PriorityQueue<Integer>();
			    				for(int i=1;i<=n;i++){
			    					if(indeg[i]==0){
			    						q.add(i);
			    					}
			    				}
			    				while(!q.isEmpty()){
			    					int top=q.poll();
			    					st.push(top);
			    					for(Node i:adj[top]){
			    						indeg[i.to]--;
			    						if(indeg[i.to]==0){
			    							q.add(i.to);
			    						}
			    					}
			    				}
			    		    }
			    		        
			    		        static int state=1;
			    		        static long no_exc=0,no_vert=0;
			    		      static Stack<Integer> st;
			    		      static HashSet<Integer> inset;
			    		     /*   private static void topo(int curr){
			    		        	
			    		        	Visited[curr]=true;
			    		        	inset.add(curr);
			    		        	for(int x:adj[curr]){
			    		        		if(adj[x].contains(curr) || inset.contains(x)){
			    		        			state=0;
			    		        			return;
			    		        		}
			    		        		if(state==0)
			    		        			return;
			    		        		
			    		        	}
			    		        	st.push(curr);
			    		        	
			    		        	inset.remove(curr);
			    		        }*/
			    		        static HashSet<Integer> hs;
			    		       
			    		     
			    		     	static boolean prime[];
								static int spf[];
								public static void sieve(int n){
									prime=new boolean[n+1];
									spf=new int[n+1];
									
									Arrays.fill(spf, 1);
									Arrays.fill(prime, true);
								prime[1]=false;
									spf[2]=2;
									
								for(int i=4;i<=n;i+=2){
									spf[i]=2;
								}
								for(int i=3;i<=n;i+=2){
									if(prime[i]){
										spf[i]=i;
										for(int j=2*i;j<=n;j+=i){
											
											prime[j]=false;
										if(spf[j]==1){
											spf[j]=i;
										}
										}
									}
								}
								
									
								}
			    		     	
			    		    	// To Get Input
			// Some Buffer Methods
			 
			    		     	public static void sort(long a[]){
			    		     		Merge(a, 0, a.length-1);
			    		     	}
			    		    	public static void InputReader(InputStream stream1) {
			    		    		stream = stream1;
			    		    	}
			 
			    		    	private static boolean isWhitespace(int c) {
			    		    		return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
			    		    	}
			 
			    		    	private static boolean isEndOfLine(int c) {
			    		    		return c == '\n' || c == '\r' || c == -1;
			    		    	}
			 
			    		    	private static int read() {
			    		    		if (numChars == -1)
			    		    			throw new InputMismatchException();
			    		    		if (curChar >= numChars) {
			    		    			curChar = 0;
			    		    			try {
			    		    				numChars = stream.read(buf);
			    		    			} catch (IOException e) {
			    		    				throw new InputMismatchException();
			    		    			}
			    		    			if (numChars <= 0)
			    		    				return -1;
			    		    		}
			    		    		return buf[curChar++];
			    		    	}
			 
			    		    	private static int nextInt() {
			    		    		int c = read();
			    		    		while (isSpaceChar(c))
			    		    			c = read();
			    		    		int sgn = 1;
			    		    		if (c == '-') {
					sgn = -1;
					c = read();
				}
				int res = 0;
				do {
					if (c < '0' || c > '9')
						throw new InputMismatchException();
					res *= 10;
					res += c - '0';
			    		    			c = read();
			    		    		} while (!isSpaceChar(c));
			    		    		return res * sgn;
			    		    	}
			 
			    		    	private static long nextLong() {
			    		    		int c = read();
			    		    		while (isSpaceChar(c))
			    		    			c = read();
			    		    		int sgn = 1;
			    		    		if (c == '-') {
					sgn = -1;
					c = read();
				}
				long res = 0;
				do {
					if (c < '0' || c > '9')
						throw new InputMismatchException();
					res *= 10;
					res += c - '0';
			    		    			c = read();
			    		    		} while (!isSpaceChar(c));
			    		    		return res * sgn;
			    		    	}
			 
			    		    	private static String nextToken() {
			    		    		int c = read();
			    		    		while (isSpaceChar(c))
			    		    			c = read();
			    		    		StringBuilder res = new StringBuilder();
			    		    		do {
			    		    			res.appendCodePoint(c);
			    		    			c = read();
			    		    		} while (!isSpaceChar(c));
			    		    		return res.toString();
			    		    	}
			 
			    		    	private static String nextLine() {
			    		    		int c = read();
			    		    		while (isSpaceChar(c))
			    		    			c = read();
			    		    		StringBuilder res = new StringBuilder();
			    		    		do {
			    		    			res.appendCodePoint(c);
			    		    			c = read();
			    		    		} while (!isEndOfLine(c));
			    		    		return res.toString();
			    		    	}
			 
			    		    	private static int[] nextIntArray(int n) {
			    		    		int[] arr = new int[n];
			    		    		for (int i = 0; i < n; i++) {
			    		    			arr[i] = nextInt();
			    		    		}
			    		    		return arr;
			    		    	}
			 
			    		    	private static long[][] next2dArray(int n, int m) {
			    		    		long[][] arr = new long[n][m];
			    		    		for (int i = 0; i < n; i++) {
			    		    			for (int j = 0; j < m; j++) {
			    		    				arr[i][j] = nextLong();
			    		    			}
			    		    		}
			    		    		return arr;
			    		    	}
			    		    	private static char[][] nextCharArray(int n,int m){
			    		    		char [][]c=new char[n][m];
			    		    		for(int i=0;i<n;i++){
			    		    			String s=nextLine();
			    		    			for(int j=0;j<s.length();j++){
			    		    				c[i][j]=s.charAt(j);
			    		    			}
			    		    		}
			    		    		return c;
			    		    	}
			 
			    		    	private static long[] nextLongArray(int n) {
			    		    		long[] arr = new long[n];
			    		    		for (int i = 0; i < n; i++) {
			    		    			arr[i] = nextLong();
			    		    		}
			    		    		return arr;
			    		    	}
			 
			    		    	private static void pArray(int[] arr) {
			    		    		for (int i = 0; i < arr.length; i++) {
			    		    			pw.print(arr[i] + " ");
			    		    		}
			    		    		pw.println();
			    		    		return;
			    		    	}
			 
			    		    	private static void pArray(long[] arr) {
			    		    		for (int i = 0; i < arr.length; i++) {
			    		    			pw.print(arr[i] + " ");
			    		    		}
			    		    		pw.println();
			    		    		return;
			    		    	}
			 
			    		    	private static void pArray(boolean[] arr) {
			    		    		for (int i = 0; i < arr.length; i++) {
			    		    			pw.print(arr[i] + " ");
			    		    		}
			    		    		pw.println();
			    		    		return;
			    		    	}
			 
			    		    	private static boolean isSpaceChar(int c) {
			    		    		if (filter != null)
			    		    			return filter.isSpaceChar(c);
			    		    		return isWhitespace(c);
			    		    	}
			 
			    		    	private interface SpaceCharFilter {
			    		    		public boolean isSpaceChar(int ch);
			    		    	}
			    		    	
			
			}
			    		    
			    		        class Node{
			    		    	int to;
			    		    	long dist;
			    		    	Node(int to,long dist){
			    		    		this.to=to;
			    		    		this.dist=dist;
			    		    	}
			    		    	
			    		    }
			    		        class Qu{
			    		    		long a0,a1,a2,a3;
			    		    		public Qu(long a0,long a1,long a2,long a3) {
			    		    			this.a0=a0;
			    		    			this.a1=a1;
			    		    			this.a2=a2;
			    		    			this.a3=a3;
			    		    		}
			    		    }
			    		
			class Dsu{
			private int rank[], parent[] ,n;
			long str[],si[],larg[];
			long max=0;
			int cnt=0;
			private static int[] parent1;
			Dsu(int size){
				this.n=size+1;
				rank=new int[n];
				cnt=n-1;
				//parent=new int[n];
			    		    		    		parent=new int[n];
			    		    		    		str=new long[n];
			    		    		    		si=new long[n];
			    		    		
			    		    		    		larg=new long[n];
			    		    		    		makeSet();
			    		    		
			    		    		    	}
			    		    		    	
			    		    		    	void makeSet(){
			    		    		    		for(int i=0;i<n;i++){
			    		    		    			parent[i]=i;
			    		    		    			si[i]=1;
			    		    		    		}
			    		    		    	}
			    		    		    	
			    		    		    	int find(int x){
			    		    		    		if(parent[x]!=x){
			    		    		    			
			    		    		    			parent[x]=find(parent[x]);
			    		    		    		}
			    		    		    		return parent[x];
			    		    		    	}
			    		    		    	
			    		    		    	void join(int ind,long val){
			    		    		    		if(str[ind]==0){
			    		    		    			str[ind]=val;
			    		    		    			larg[ind]=val;
			    		    		    			max=Math.max(max, str[ind]);
			    		    		    		}
			    		    		    		int prev_ind=(ind-1);
			    		    		    		int next_ind=(ind+1);
			    		    		    		if(prev_ind>0 && larg[prev_ind]!=0){
			    		    		    			union(prev_ind,ind);
			    		    		    		}
			    		    		    		if(next_ind<n && larg[next_ind]!=0){
			    		    		    			union(next_ind,ind);
			    		    		    		}
			    		    		    		
			    		    		    	}
			    		    		    
			    		    		    	
			    		    		    	boolean union(int x,int y){
			    		    		    		int xRoot=find(x);
			    		    		    		int yRoot=find(y);
			    		    		    
			    		    		    	
			    		    		    		if(xRoot==yRoot)
			    		    		    			return false;
			    		    		    		if(rank[xRoot]<rank[yRoot]){
			    		    		    		parent[xRoot]=yRoot;
			    		    		    		
			    		    		    		larg[yRoot]=Math.max(larg[xRoot], larg[yRoot]);
			    		    		    		
			    		    		    		si[yRoot]+=si[xRoot];
			    		    		    		str[yRoot]=larg[yRoot]*si[yRoot];
			    		    		    			max=Math.max(str[yRoot], max);
			    		    		    		}else if(rank[yRoot]<rank[xRoot]){
			    		    		    			parent[yRoot]=xRoot;
			     
			    		    		    			larg[xRoot]=Math.max(larg[xRoot], larg[yRoot]);
			        		    		    		
			        		    		    		si[xRoot]+=si[yRoot];
			        		    		    		str[xRoot]=larg[xRoot]*si[xRoot];
			    			    		    		max=Math.max(str[xRoot], max);
			    		    		    		}else{
			    		    		    			parent[yRoot]=xRoot;
			    		    		    			rank[xRoot]++;
			     
			    		    		    			larg[xRoot]=Math.max(larg[xRoot], larg[yRoot]);
			        		    		    		
			        		    		    		si[xRoot]+=si[yRoot];
			        		    		    		str[xRoot]=larg[xRoot]*si[xRoot];
			    			    		    		max=Math.max(str[xRoot], max);
			    		    		    		
			    		    		    		}
			    		    		    		cnt--;
			    		    		    		return true;
			    		    		    	}
			    	
			    		    		     
			    		    		    }
		class Pair1 implements Comparable<Pair1>{
				long l,b;
				Pair1(long l,long b){
					this.l=l;
					this.b=b;
				}
				@Override
				public int compareTo(Pair1 arg0) {
					if(arg0.l == l){
						long area1 = arg0.l * arg0.b;
						long area2 = l * b;
						return (int)(area1 - area2);
					}
					return (int)(l - arg0.l);
						
					
				}
			
			
			}
			  
			
