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.concurrent.DelayQueue;    
          public class Main
           {
            private InputStream is;
            private PrintWriter out;
            static int MOD = (int)(1e9+7);
            ArrayList<Integer>[] amp;
            public static void main(String[] args) throws Exception
            {
                new Thread(null, new Runnable()
                {
                public void run()
                {
                    try {
         } catch (Exception e)
                    {
                        System.out.println(e);
                    }
                }
            }, "1", 1 << 26).start();
                new Main().soln();
            }
            char ch[][];
            static ArrayList<Integer>[] g=new ArrayList[100001];
            static ArrayList<Integer> ar[];
            static long ok[];    
            static int phi[]=new int[500005];
            static int dp[][];
            void solve()
            {
            	int n = ni();
            	int k = ni();
            	int a[] = na(n);
            	int count = 0;
            	HashMap<Integer,Integer> hm = new HashMap();
            	for(int i=0;i<n;i++){
            		if(!hm.containsKey(a[i]))
            			hm.put(a[i],1);
            		else
            			hm.put(a[i],hm.get(a[i])+1);
            	}
            	
            	for(int x:hm.keySet()){
            		if(hm.get(x)>=2){
            			out.println(0);
            			return;
            		}
            	}
            		
            	for(int i=0;i<n;i++){
            		int x = a[i]&k;
            		if(x!=a[i]&&hm.containsKey(x)){
            			out.print(1);
            			return;
            		}
            	}
            	
            	for(int i=0;i<n;i++){
            		a[i] = a[i]&k;
            	}
            	
            	HashMap<Integer,Integer> hm2 = new HashMap();
            	
            	
            	for(int i=0;i<n;i++){
            		if(!hm2.containsKey(a[i]))
            			hm2.put(a[i],1);
            		else
            			hm2.put(a[i],hm2.get(a[i])+1);
            	}
            	
            	
            	
            	for(int x:hm2.keySet()){
            		if(hm2.get(x)>=2){
            			out.println(2);
            			return;
            		}
            	}
            	
            	out.print(-1);
            }
            
            
            public static void reverse()
            {
            	
            }
            
            public static boolean check(long n,long k)
            {
            	long ans = 0;
            	long start=n/2;
            	while(n>0)
            	{
            		ans+=Math.min(n,k);
            		n-=k;
            		n-=(n/10);
            	}
            	return (ans>=start);
            }
            
            public static void permute(String s,int l,int r)
            {
            	if(l == r)
            	{
            		System.out.println(s);
            	}
            	else
            	{
            		for(int i=l;i<=r;i++)
            		{
            			s = swap(s,l,i);
            			permute(s,l+1,r);
            			s = swap(s,l,i);
            		}
            	}
            }
             
            public static String swap(String s,int l,int r)
            {
            	char c[] = s.toCharArray();
            	char temp = c[l];
            	c[l] = c[r];
            	c[r] = temp;
            	return new String(c);
            }
            
            public static long query(int v,int start,int end,int l,int r,int x)
            {
            	if(r < start || end < l)
                {
                    return 0;
                }
                if(l <= start && end <= r)
                {
                    return (tre[v]);
                }
                int mid = (start + end) / 2;
                long p1 = query(2*v, start, mid, l, r,x);
                long p2 = query(2*v+1, mid+1, end, l, r,x);
                return p1+p2;	
            }
            public static void update(int v,int tl,int tr,long l,long harami2)
            {
            	if(tl==tr)
                {
                    tre[v]=harami2;
                }
                else
                {
                    int mid=(tl+tr)/2;
                    if(tl <= l &&l <= mid)
                    {
                        update(2*v,tl, mid, l, harami2);
                    }
                    else
                    {
                        update(2*v+1,mid+1,tr, l, harami2);
                    }
                    tre[v]=tre[2*v]+tre[2*v+1];
                }
            }
            static long tre[]=new long[8000005];
            static ArrayList<String> dictionary = new ArrayList();
            public static void wordBreakUtil(String s,int n,String result)
            {
            	for(int i=1;i<=n;i++)
            	{
            		String prefix = s.substring(0,i);
            		if(dictionary.contains(prefix))
            		{
            			if(i==n)
            			{
            				result+=prefix;
            				System.out.println(result);
            				return;
            			}
            			wordBreakUtil(s.substring(i),n-i,result+prefix+" ");
            		}
            	}
            }
            public static void permute(char s[],int l,int r)
            {
            	if(l==r)
            	{
            		System.out.println(new String(s));
            	}
            	else
            	{
            		for(int i=l;i<=r;i++)
            		{
            			char temp=s[i];
            			s[i]=s[l];
            			s[l]=temp;
            			permute(s,l+1,r);
            			temp=s[i];
            			s[i]=s[l];
            			s[l]=temp;
            		}
            	}
            }
            public static void StockSpan(int a[],int n)
            {
            	Stack<Integer> st = new Stack();
            	st.push(0);
            	int S[]=new int[n];
            	S[0]=1;
            	for(int i=1;i<n;i++)
            	{
            		while(!st.isEmpty()&&a[st.peek()]<=a[i])
            			st.pop();
            		S[i]=(st.isEmpty())?(i+1):(i-st.peek());
            		st.push(i);
            	}
            	for(int i=0;i<n;i++)
            		System.out.print(S[i]+" ");
            }
            
            
            public static void MaxSum(int a[][],int r,int c)
            {
            	int ans=0;
            	for(int i=0;i<r/2;i++)
            	{
            		for(int j=0;j<c/2;j++)
            		{
            			int r1=i;
            			int c1=j;
            			int r2=r-i-1;
            			int c2=c-j-1;
            			ans+=Math.max(Math.max(a[r1][c1],a[r1][c2]),Math.max(a[r2][c1],a[r2][c2]));
            		}
            	}
            	System.out.println(ans);
            
            }
            
            
            public static void Dia(int a[][],int row,int col)
            {
            	for(int line=1;line<=(row+col-1);line++)
            	{
            		int start_col = Math.max(0,line-row);
            		int count = Math.min(line,Math.min(row,col-start_col));
            		for(int j=0;j<count;j++)
            		{
            			System.out.print(a[Math.min(row,line)-j-1][start_col+j]+" ");
            		}
            		System.out.println();
            	}
            }

			public static void AntiClock(int a[][],int n)
            
            {
            	for(int i=0;i<n;i++)
            	{
            		for(int j=i;j<n;j++)
            		{
            			int tmp=a[i][j];
            			a[i][j]=a[j][i];
            			a[j][i]=tmp;
            		}
            	}
            	for(int i=0;i<n/2;i++)
            	{
            		for(int j=0;j<n;j++)
            		{
            			int tmp=a[i][j];
            			a[i][j]=a[n-1-i][j];
            			a[n-1-i][j]=tmp;
            		}
            	}
            	
            }
            
           
            
            
            
            
            public static long pr(long x,long y,long m)
            {
            	if(y==0)
            		return 1;
            	long p = pr(x,y/2,m);
            	p=(p*p)%m;
            	return(y%2==0)?(p):(x*p%m);
            }
            public static long GCD(long x,long y)
            {
            	if(y==0)
            		return x;
            	else
            		return GCD(y,x%y);
            }
            
            public static void print(ArrayList<Integer> ar)
            {
            	Collections.sort(ar,Collections.reverseOrder());
            	System.out.println("Yes");
            	for(int x:ar)
            	{
            		System.out.print(x+" ");
            	}
            	return;
            }
            public static void LOL()
            {
            	/*int a[]=new int[5];
            	a[0]=2;a[1]=1;a[2]=4;a[3]=3;a[4]=5;
            	 System.out.println(LIS(a,5));
            	 int n=5;
            	 int dp[]=new int[n];
            	 for(int i=0;i<n;i++)
            		 dp[i]=1;
            	 
            	 int backtrack[]=new int[n];
            	 Arrays.fill(backtrack,-1);
            	 for(int i=1;i<n;i++)
            	 {
            		 for(int j=0;j<i;j++)
            		 {
            			 if(dp[j]+1>dp[i]&&a[j]<a[i])
            			 {
            				 dp[i]=dp[j]+1;
            				 backtrack[i]=j;
            			 }
            		 }
            	 }
            	 int index=-1;
            	 int max=0;
            	 for(int i=0;i<n;i++)
            	 {
            		 if(max<dp[i])
            		 {
            			 index=i;
            			 max=dp[i];
            		 }
            	 }
            	 
            	 int tmp=index;
            	 Stack<Integer> st=new Stack();
            	 while(tmp>=0)
            	 {
            		 st.push(a[tmp]);
            		 tmp=backtrack[tmp];
            	 }
            	 while(!st.isEmpty())
            	 {
            		 out.print(st.pop()+" ");
            	 }
            /*	int n=150;
            	int ugly[]=new int[n+1];
            	ugly[0]=1;
            	int next_multiple_of_2=2;
            	int next_multiple_of_3=3;
            	int next_multiple_of_5=5;
            	int i2=0;int i3=0;int i5=0;
            	for(int i=1;i<n;i++)
            	{
            		int min=Math.min(next_multiple_of_5, Math.min(next_multiple_of_3, next_multiple_of_2));
            		ugly[i]=min;
            		if(min==next_multiple_of_2)
            		{
            			i2++;
            			next_multiple_of_2=ugly[i2]*2;
            		}
            		if(min==next_multiple_of_3)
            		{
            			i3++;
            			next_multiple_of_3=ugly[i3]*3;
            		}
            		if(min==next_multiple_of_5)
            		{
            			i5++;
            			next_multiple_of_5=ugly[i5]*5;
            		}
            	}
            	System.out.println(ugly[n-1]);
            	
            	int t=ni();
            	while(t-->0)
            	{
            		long n=nl();
            		int a[]=new int[4];
            		a[0]=2;
            		a[1]=3;
            		a[2]=5;
            		a[3]=7;
            		long sucks=0;
            		for(int i=0;i<(1<<4);i++)
            		{
            			int count=0;
            			long curr=1;
            			for(int j=0;j<4;j++)
            			{
            				int x=i;
            				x&=(1<<j);
            				if(x>0)
            				{
            					curr*=(long)a[j];
            					count++;
            				}
            			}
            			if(count==0)
            				continue;
            			if(count%2==1)
            			{
            				sucks+=(n/curr);
            			}
            			else
            			{
            				sucks-=(n/curr);
            			}
            		}
            		out.println(n-sucks);
            	}
            	String s1=ns();
            	String s2=ns();
            	int m=s1.length();int n=s2.length();
            	int dp[][]=new int[m+1][n+1];
            	for(int i=0;i<=m;i++)
            	{
            		for(int j=0;j<=n;j++)
            		{
            			if(i==0)
            				dp[i][j]=j;
            			else if(j==0)
            				dp[i][j]=i;
            			else if(s1.charAt(i-1)==s2.charAt(j-1))
            				dp[i][j]=dp[i-1][j-1];
            			else
            				dp[i][j]=1+Math.min(dp[i-1][j-1],Math.min(dp[i-1][j],dp[i][j-1]));
            		}
            	}*/
            }
            public static int edit(String s1,String s2,int m,int n)
            {
            	if(m==0)
            		return n;
            	if(n==0)
            		return m;
            	if(s1.charAt(m-1)==s2.charAt(n-1))
            		return edit(s1,s2,m-1,n-1);
            	return 1+Math.min(edit(s1,s2,m,n-1),Math.min(edit(s1,s2,m-1,n),edit(s1,s2,m-1,n-1)));
            }
            static int max=1;
            public static int LIS(int a[],int n  )
            {
            	if(n==1)
            		return 1;
            	int res=1;
            	int max_ending_here=1;
            	for(int i=1;i<n;i++)
            	{
            		res=LIS(a,i);
            		if(a[i-1]<a[n-1]&&res+1>max_ending_here)
            			max_ending_here=res+1;
            	}
            	max=Math.max(max,max_ending_here);
            	return max_ending_here;
            }
            static boolean visi1[];
            static int cont=0;
            static int para[];
            public static void dfs(int curr,int pr)
            {
            	visi1[curr]=true;
            	
            	int trees=0;
            	for(int x:g[curr])
            	{
            		if(!visi1[x]&&x!=pr)
            		{
            			trees++;
            			dfs(x,pr);
            		}
            	}
            	if(trees==0)cont++;
            }
            
            static boolean visited[][];
			static int a[][];
            
          /* public static int find(int v,int start,int end,int l,int r)
            {
                if(r < start || end < l)
                {
                    return Integer.MIN_VALUE;
                }
                if(l <= start && end <= r)
                {
                    return (tre[v]);
                }
                int mid = (start + end) / 2;
                int p1 = find(2*v, start, mid, l, r);
                int p2 = find(2*v+1, mid+1, end, l, r);
                return Math.max(p1, p2);          
            }
            static int tre[]=new int[4000005];
            public static void Update(int v,int tl,int tr,int index,int val)
            {
                if(tl==tr)
                {
                    tre[v]=val;
                }
                else
                {
                    int mid=(tl+tr)/2;
                    if(tl <= index &&index <= mid)
                    {
                        Update(2*v,tl, mid, index, val);
                    }
                    else
                    {
                        Update(2*v+1,mid+1,tr, index, val);
                    }
                    tre[v]=(Math.max(tre[2*v],tre[2*v+1]));
                }
            }
            */
            
            static int d,x,y;
            static void exE(int a,int b)
            {
            	if(b==0)
            	{
            		d=a;
            		x=1;
            		y=0;
            	}
            	else
            	{
            		exE(b,a%b);
            		int tmp=x;
            		x=y;
            		y=tmp - (a/b)*y;
            	}
            }
            boolean isPrime(long curr)
                {
                if(curr==0||curr==1)
                    return false;
                for(long i = 2;i*1L*i<=curr;i++) if(curr%i==0) return false;
                return true;
            }
            int  p ;
            long modInverse(long a, long mOD2){
                return  power(a, mOD2-2, mOD2);
            }
            long power(long x, long y, long m)
            {
            if (y == 0)
            return 1;
            long p = power(x, y/2, m) % m;
            p = (p * p) % m;
        
            return (y%2 == 0)? p : (x * p) % m;
            }
            public static long gcd(long a, long b){
                if(b==0) return a;
                return gcd(b,a%b);
            }
            class Pair1 implements Comparable<Pair1>{
                int a;
                int b;
                Pair1(int a,int b){
                	this.a = a;
                	this.b = b;
                }
                public int hashCode() {
                    return Objects.hash();
                }
                
                @Override
                public int compareTo(Pair1 arg0) {
                    if(b!=arg0.b)
                    	return (int)(arg0.b-b);
                    else
                    	return (int)(a-arg0.a);
                }    
            }
            long power(long x, long y, int mod){
                long ans = 1;
                while(y>0){
                    if(y%2==0){
                        x = (x*x)%mod;
                        y/=2;
                    }
                    else{
                        ans = (x*ans)%mod;
                        y--;
                    }
                }
                return ans;
            }
            void soln() {
                is = System.in;
                out = new PrintWriter(System.out);
                long s = System.currentTimeMillis();
                solve();
                out.flush();
            }
             private byte[] inbuf = new byte[1024];
            public int lenbuf = 0, ptrbuf = 0;
            private int readByte() {
                if (lenbuf == -1)
                    throw new InputMismatchException();
                if (ptrbuf >= lenbuf) {
                    ptrbuf = 0;
                    try {
                        lenbuf = is.read(inbuf);
                    } catch (IOException e) {
                        throw new InputMismatchException();
                    }
                    if (lenbuf <= 0)
                        return -1;
                }
                return inbuf[ptrbuf++];
            }
            private boolean isSpaceChar(int c) {
                return !(c >= 33 && c <= 126);
            }
            private int skip() {
                int b;
                while ((b = readByte()) != -1 && isSpaceChar(b))
                    ;
                return b;
            }
            private double nd() {
                return Double.parseDouble(ns());
            }
            private char nc() {
                return (char) skip();
            }
            private String ns() {
                int b = skip();
                StringBuilder sb = new StringBuilder();
                while (!(isSpaceChar(b))) {
                    sb.appendCodePoint(b);
                    b = readByte();
                }
                return sb.toString();
            }
            private char[] ns(int n) {
                char[] buf = new char[n];
                int b = skip(), p = 0;
                while (p < n && !(isSpaceChar(b))) {
                    buf[p++] = (char) b;
                    b = readByte();
                }
                return n == p ? buf : Arrays.copyOf(buf, p);
            }
            private int[][] nm(int n, int m) {
                int[][] map = new int[n][m];
                for (int i = 0; i < n; i++)
                {
                    for(int j=0;j<m;j++)
                        map[i][j]=ni();
                }
                return map;
            }
            private int[] na(int n) {
                int[] a = new int[n];
                for (int i = 0; i < n; i++)
                    a[i] = ni();
                return a;
            }
            private int ni() {
                int num = 0, b;
                boolean minus = false;
                while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
                    ;
                if (b == '-') {
                    minus = true;
                    b = readByte();
                }
                while (true) {
                    if (b >= '0' && b <= '9') {
                        num = num * 10 + (b - '0');
                    } else {
                        return minus ? -num : num;
                    }
                    b = readByte();
                }
            }
            private long nl() {
                long num = 0;
                int b;
                boolean minus = false;
                while ((b = readByte()) != -1 && !((b >= '0' && b <= '9') || b == '-'))
                    ;
                if (b == '-') {
                    minus = true;
                    b = readByte();
                }
                while (true) {
                    if (b >= '0' && b <= '9') {
                        num = num * 10 + (b - '0');
                    } else {
                        return minus ? -num : num;
                    }
                    b = readByte();
                }
            }
            private boolean oj = System.getProperty("ONLINE_JUDGE") != null;
            private void tr(Object... o) {
                if (!oj)
                    System.out.println(Arrays.deepToString(o));
            }
        }  