Let's call two numbers similar if their binary representations contain the same number of digits equal to 1. For example:

  * 2 and 4 are similar (binary representations are 10 and 100); 
  * 1337 and 4213 are similar (binary representations are 10100111001 and 1000001110101); 
  * 3 and 2 are not similar (binary representations are 11 and 10); 
  * 42 and 13 are similar (binary representations are 101010 and 1101). 



You are given an array of n integers a_1, a_2, ..., a_n. You may choose a non-negative integer x, and then get another array of n integers b_1, b_2, ..., b_n, where b_i = a_i ⊕ x (⊕ denotes bitwise XOR).

Is it possible to obtain an array b where all numbers are similar to each other?

Input

The first line contains one integer n (2 ≤ n ≤ 100).

The second line contains n integers a_1, a_2, ..., a_n (0 ≤ a_i ≤ 2^{30} - 1).

Output

If it is impossible to choose x so that all elements in the resulting array are similar to each other, print one integer -1.

Otherwise, print any non-negative integer not exceeding 2^{30} - 1 that can be used as x so that all elements in the resulting array are similar.

Examples

Input


2
7 2


Output


1


Input


4
3 17 6 0


Output


5


Input


3
1 2 3


Output


-1


Input


3
43 12 12


Output


1073709057
import java.io.*;
import java.util.*;
import java.awt.Point;

public class CF_1257F {
    static final String name = "CF_1257F";
    static final boolean test = new File(name + ".in").exists();

    public static void main(String args[]) throws Exception {
        BufferedScanner in = new BufferedScanner(test ? new FileInputStream(name + ".in") : System.in);
        BufferedPrinter out = new BufferedPrinter(test ? new FileOutputStream(name + ".out") : System.out);

        int n = in.nextInt();
        int[] a = in.nextN(n);

        solve(a, n, out);

        out.close();
        in.close();
    }

    static void solve(int[] a, int n, BufferedPrinter out){
        HashMap<Long, Integer> v = new HashMap<>();
        for(int i = 0; i < 1 << 15; i++){
            long hash = 0;
            long base = Long.bitCount(a[0] & (1 << 15) - 1 ^ i) - 1000;
            for(int j = 0; j < n; j++){
                long curr = Long.bitCount(a[j] & (1 << 15) - 1 ^ i) - base;
                hash = hash * 100007 + curr;
            }

            v.put(hash, i);
        }

        for(int i = 0; i < 1 << 15; i++){
            long hash = 0;
            long base = 1000 + Long.bitCount(a[0] >> 15 ^ i);

            for(int j = 0 ; j < n; j++){
                long curr = base - Long.bitCount(a[j] >> 15 ^ i);
                hash = hash * 100007 + curr;
            }

            if(v.containsKey(hash)){
                out.println((i << 15) + v.get(hash));
                return;
            }
        }

        out.println(-1);
    }


    /**
     * My template below. FastIO and utility functions.
     * Minimized with https://codebeautify.org/javaviewer.
     */

    // @formatter:off
    static<T>ArrayList<ArrayList<T>>get2D(int n){ArrayList<ArrayList<T>>ret=new ArrayList<>();for(int i=0;i<n;i++)ret.add(new ArrayList<>());return ret;}
    static void force(boolean condition){if(!condition)throw new IllegalStateException();}
    static void debug(Object obj){if(obj instanceof long[][]){for(long[]a:(long[][])obj)System.out.println(Arrays.toString(a));}
    else if(obj instanceof int[][]){for(int[]a:(int[][])obj)System.out.println(Arrays.toString(a));}
    else if(obj instanceof char[][]){for(char[]a:(char[][])obj)System.out.println(Arrays.toString(a));}
    else if(obj instanceof boolean[][]){for(boolean[]a:(boolean[][])obj)System.out.println(Arrays.toString(a));}
    else if(obj instanceof long[]){System.out.println(Arrays.toString((long[])obj));}
    else if(obj instanceof int[]){System.out.println(Arrays.toString((int[])obj));}
    else if(obj instanceof char[]){System.out.println(Arrays.toString((char[])obj));}
    else if(obj instanceof boolean[]){System.out.println(Arrays.toString((boolean[])obj));}
    else{System.out.println(obj);}}
    static class BufferedPrinter{PrintWriter out;BufferedPrinter(OutputStream out){this(new OutputStreamWriter(out));}
    BufferedPrinter(Writer out){this.out=new PrintWriter(new BufferedWriter(out));}
    void print(Object...os){for(int i=0;i<os.length;i++){if(i!=0)out.print(' ');out.print(os[i]);}}
    void println(Object...os){print(os);out.println();}
    void close(){out.close();}
    void flush(){out.flush();}}
    static class BufferedScanner{private final InputStream in;private final byte[]buf=new byte[1<<13];int pos,count;BufferedScanner(InputStream in)throws IOException{this.in=in;}
    long nextLong()throws IOException{return Long.parseLong(next());}
    int[]nextN(int n)throws IOException{int[]ret=new int[n];for(int i=0;i<n;i++)ret[i]=this.nextInt();return ret;}
    long[]nextNL(int n)throws IOException{long[]ret=new long[n];for(int i=0;i<n;i++)ret[i]=this.nextLong();return ret;}
    private int read(){if(count==-1)err();try{if(pos>=count){pos=0;count=in.read(buf);if(count<=0)return-1;}}catch(IOException e){err();}
    return buf[pos++];}
    private static boolean isSpace(int c){return c==' '||c=='\n'||c=='\r'||c=='\t'||c==-1;}
    private int readSkipSpace(){int ret;do{ret=read();}while(isSpace(ret));return ret;}
    int nextInt(){int sign=1;int c=readSkipSpace();if(c=='-'){sign=-1;c=read();}
    int ret=0;do{if(c<'0'||c>'9')err();ret=ret*10+c-'0';c=read();}while(!isSpace(c));return sign*ret;}
    String next(){StringBuilder sb=new StringBuilder();int c=readSkipSpace();do{sb.append((char)c);c=read();}while(!isSpace(c));return sb.toString();}
    private void err(){throw new InputMismatchException();}
    void close()throws IOException{in.close();}}
    // @formatter:on
}
