Xor Pyramid

• Time limit: 1.00 s
• Memory limit: 512 MB

Consider a xor pyramid where each number is the xor of lower-left and lower-right numbers. Here is an example pyramid:

Given the bottom row of the pyramid, your task is to find the topmost number.

Input

The first input line has an integer $n$: the size of the pyramid.

The next line has $n$ integers $a_1,a_2,\dots,a_n$: the bottom row of the pyramid.

Output

Print one integer: the topmost number.

Constraints

• $1 \le n \le 2 \cdot 10^5$
  
• $1 \le a_i \le 10^9$
  

Example

Input:
8
2 10 5 12 9 5 1 5

Output:
9