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No.699 Let's Form Teams in Pairs 2

レベル : / AI推定難易度 : 800 / 実行時間制限 : 1ケース 1.000秒 / メモリ制限 : 512 MB / 標準ジャッジ問題
タグ : （AC するまで非表示） / 解いたユーザー数 100
作問者 : nmnmnmnmnmnmnm
お気に入りにしたユーザー ProblemId : 2332 / 自分の提出
問題文最終更新日: 2026-06-27 22:02:00
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Problem Statement

$N$ players ($N$ is even) form one team and take on some kind of battle.
The combat power of the $i$-th player is $A_i$.

Each of the $N$ players must form a pair of 2 people.
When a pair is formed, its combat power is the value obtained by adding the combat powers of its players.

The XOR of the combat powers of all pairs is the combat power of the team.
What is the maximum combat power of the team when the pairs are chosen optimally?

Input

$N$
$A_0$ $A_1$ $\dots$ $A_{N-1}$

$N$ is a positive integer ($N$ is even). $2 \le N \le 14$.
$A_i$ is a positive integer. $1 \le A_i \le 1000000000=10^9$.

Output

Output the answer on one line.
Print a newline at the end.

Sample

Sample 1
Input
4
1 2 3 4
Output
4

If the player with combat power 1 and the player with combat power 2 form a pair, the combat power of the pair is 3.
If the player with combat power 3 and the player with combat power 4 form a pair, the combat power of the pair is 7.
In this case, the combat power of the team is the XOR of the combat powers of the pairs, which is 4, and this is the maximum.

Sample 2
Input
4
1 1 1 1
Output
0

No matter how the pairs are formed, the combat power of the team is 0.
Forming pairs may result in a combat power lower than that of the individual players.
However, the pairs must be formed.

Sample 3
Input
10
387 137 192 123 29 193 753 210 821 437
Output
2044

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