Deception

Seunghyun likes tricking people. Today he wants to trick us with a sequence.

Seunghyun brought a sequence of $n$ natural numbers $a_1, a_2, \dots, a_n$. He then tells us to put each element of the sequence into group X or group Y. Call the elements of X $X_1, X_2, \dots, X_k$ and the elements of Y $Y_1, Y_2, \dots, Y_{n-k}$. Neither group may be empty, so $k > 0$ and $n - k > 0$.

If $X_1 \oplus X_2 \oplus \dots \oplus X_k$ equals $Y_1 \oplus Y_2 \oplus \dots \oplus Y_{n-k}$, Seunghyun pays us $X_1 + X_2 + \dots + X_k$ won.

He has tricked us so often that we do not believe him, but there is no way to lose money here, so we will try once. Given the sequence $a$ that Seunghyun presents, write a program that decides whether we can get paid, and if we can, finds the largest amount.

$\oplus$ is the bitwise exclusive or (XOR). Write both numbers in binary, then put 1 in each position where the two bits differ and 0 where they are the same.

The first line contains $n$ ($1 \le n \le 1000$). The second line contains $a_1, a_2, \dots, a_n$ ($1 \le a_i \le 10^6$), separated by spaces.

Print the largest amount of money you can receive on the first line. Print 0 if you cannot receive any money.