Yet Another Minimax Problem

You are given non-negative integers, . We define the score for some permutation () of length to be the maximum of for .

Find the permutation with the minimum possible score and print its score.

Note: is the exclusive-OR (XOR) operator.

Input Format

The first line contains single integer, , denoting the number of integers.
The second line contains space-separated integers, , describing the respective integers.

Constraints

Output Format

Print a single integer denoting the minimum possible score.

Sample Input 0

4
1 2 3 4

Sample Output 0

Sample Input 1

3
1 2 3

Sample Output 1

Explanation

Sample Case 0:
The permutation with the minimum score is :

Because the permutation's score is the maximum of these values, we print on a new line.

Sample Case 1:
The permutation with the minimum score is :

Because the permutation's score is the maximum of these values, we print on a new line.