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
/*
If you want to aim high, aim high
Don't let that studying and grades consume you
Just live life young
******************************
If I'm the sun, you're the moon
Because when I go up, you go down
*******************************
I'm working for the day I will surpass you
https://www.a2oj.com/Ladder16.html
*/
import java.util.*;
import java.io.*;
import java.math.*;

   public class x1257F
   {
      static long MOD = 1000000021L;
      static long BASE = 37L;
      public static void main(String omkar[]) throws Exception
      {
         BufferedReader infile = new BufferedReader(new InputStreamReader(System.in));  
         StringTokenizer st = new StringTokenizer(infile.readLine());
         int N = Integer.parseInt(st.nextToken());
         int[] arr = new int[N];
         st = new StringTokenizer(infile.readLine());
         for(int i=0; i < N; i++)
            arr[i] = Integer.parseInt(st.nextToken());
         long[] pow = new long[101];
         pow[0] = 1L;
         for(int i=1; i <= 100; i++)
            pow[i] = (pow[i-1]*BASE)%MOD;
         HashMap<Long, Integer> right = new HashMap<Long, Integer>();
         for(int mask=0; mask < (1 << 15); mask++)
         {
            long hash = 0L;
            for(int i=0; i < N; i++)
               hash += (pow[i]*Integer.bitCount((mask^(arr[i] >> 15))))%MOD;
            right.put(hash%MOD, mask);
         }
         for(int mask=0; mask < (1 << 15); mask++)
         {
            int[] temp = new int[100];
            int max = 0;
            for(int i=0; i < N; i++)
            {
               temp[i] = Integer.bitCount(mask^(arr[i]%(1 << 15)));
               max = Math.max(max, temp[i]);
            }
            for(int goal=max; goal <= 30; goal++)
            {
               long hash = 0L;
               for(int i=0; i < N; i++)
                  hash += (pow[i]*(goal-temp[i]))%MOD;
               hash %= MOD;
               if(right.containsKey(hash))
               {
                  int res = mask;
                  res += right.get(hash)*(1 << 15);
                  if(works(arr, res))
                  {
                     System.out.println(res);
                     return;
                  }
               }      
            }
         }
         System.out.println(-1);
      }
      public static boolean works(int[] arr, int mask)
      {
         int N = arr.length;
         int cnt = Integer.bitCount(arr[0]^mask);
         for(int i=1; i < N; i++)
            if(cnt != Integer.bitCount(arr[i]^mask))
               return false;
         return true;
      }
   }