链接: https://cses.fi/problemset/task/2419

板块: Bitwise Operations

时限: 1.00 s ｜ 内存: 512 MB

题目描述

Consider a xor pyramid where each number is the xor of lower-left and lower-right numbers. The pyramid示意图见：https://cses.fi/file/382652cc16953396bbaeeabf0e98daec74a4bda09afb8db8da0e67870205fc76

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

输入

The first 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.

输出

Print one integer: the topmost number.

数据范围

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

样例输入

8
2 10 5 12 9 5 1 5

样例输出

9