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.util.*;
/* * */

public class _500B implements Runnable{
    public static void main(String[] args) {
	    new Thread(null, new _500B(),"Main",1<<27).start();
    }
    @Override
    public void run() {
        FastReader fd = new FastReader(System.in);
        PrintWriter out = new PrintWriter(System.out);
        int n = fd.nextInt();
        int x = fd.nextInt();
        int[] data = getArray(n,false,fd);
        HashSet<Integer> val1 = new HashSet<>(),val2 = new HashSet<>();
        int ans = Integer.MAX_VALUE;
        HashMap<Integer,Integer> mapper = new HashMap<>();
        for (int i = 0; i < n; i++){
            if(mapper.containsKey(data[i])){out.println(0);out.close();return;}
            mapper.put(data[i],i);
        }
        HashMap<Integer,Integer> andedMap = new HashMap<>();
        for(int i = 0; i < n; i++){
            int anded = data[i]&x;
            if(mapper.containsKey(anded) && mapper.get(anded) != i){
                out.println(1);out.close();
                return;
            }
            andedMap.put(anded,andedMap.getOrDefault(anded,0)+1);
        }
        for(int i : andedMap.values()){
            if(i > 1){
                out.println(2);out.close();
                return;
            }
        }

        out.println(-1);
        out.close();
    }

    //Helper functions
    static int[] getArray(int n,boolean isSorted, FastReader fd){
        int[] data = new int[n];
        for(int i = 0; i < data.length; i++){ data[i] = fd.nextInt(); }
        if(isSorted) Arrays.sort(data);
        return data;
    }
    static int gcd(int a, int b) {
        if (a == 0)
            return b;
        return gcd(b % a, a);
    }

    static void dfs(ArrayList<ArrayList<Integer>> g, boolean[] visited, int i, int N){
        for(Integer e: g.get(i)){
            if(!visited[e]){
                visited[e]=true;
                dfs(g,visited,e,N);
                //operations to be performed...
            }
        }
    }
    static int lcm(int a, int b) {
        return (a*b)/gcd(a, b);
    }

    static boolean checkDistinct(int next){// check all digits are distinct.

        String process = String.valueOf(next);
        for(int i = 0;i < process.length()-1; i++){
            String character = String.valueOf(process.charAt(i));
            if(process.substring(i+1).contains(character)){ return false; }
        }
        return true;
    }

    static int limit = (int) 1e7 + 1;
    static int[] facts = new int[limit];
    static void sieve() {  // Store the minimum prime factors of 1 to LIMIT
        facts[1] = 1;
        for (int i = 2; i < limit; i++) {
            if (i % 2 == 0 && i > 2) {
                facts[i] = 2;
            } else {
                facts[i] = i;
            }
        }
        for (int i = 3; i * i < limit; i++) {
            if (facts[i] == i) {
                for (int j = i * i; j < limit; j += i)
                    if (facts[j] == j)
                        facts[j] = i;
            }
        }
    }
    static class FastReader {
        private InputStream stream;
        private byte[] buf = new byte[1024];
        private int curChar;
        private int numChars;
        private SpaceCharFilter filter;
        private BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

        public FastReader(InputStream stream) {
            this.stream = stream;
        }

        public 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++];
        }

        public String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            }
            catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }
        public 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;
        }

        public 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;
        }

        public double nextDouble() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            int sgn = 1;
            if (c == '-') {
                sgn = -1;
                c = read();
            }
            double res = 0;
            while (!isSpaceChar(c) && c != '.') {
                if (c == 'e' || c == 'E')
                    return res * Math.pow(10, nextInt());
                if (c < '0' || c > '9')
                    throw new InputMismatchException();
                res *= 10;
                res += c - '0';
                c = read();
            }
            if (c == '.') {
                c = read();
                double m = 1;
                while (!isSpaceChar(c)) {
                    if (c == 'e' || c == 'E')
                        return res * Math.pow(10, nextInt());
                    if (c < '0' || c > '9')
                        throw new InputMismatchException();
                    m /= 10;
                    res += (c - '0') * m;
                    c = read();
                }
            }
            return res * sgn;
        }

        public String readString() {
            int c = read();
            while (isSpaceChar(c))
                c = read();
            StringBuilder res = new StringBuilder();
            do {
                res.appendCodePoint(c);
                c = read();
            }
            while (!isSpaceChar(c));

            return res.toString();
        }

        public boolean isSpaceChar(int c) {
            if (filter != null)
                return filter.isSpaceChar(c);
            return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
        }

        public String next() {
            return readString();
        }

        public interface SpaceCharFilter {
            public boolean isSpaceChar(int ch);
        }
    }
}
