CF1109A.Sasha and a Bit of Relax

Sasha likes programming. Once, during a very long contest, Sasha decided that he was a bit tired and needed to relax. So he did. But since Sasha isn't an ordinary guy, he prefers to relax unusually. During leisure time Sasha likes to upsolve unsolved problems because upsolving is very useful.

Therefore, Sasha decided to upsolve the following problem:

You have an array $a$ with $n$ integers. You need to count the number of funny pairs $(l, r)$ $(l \leq r)$. To check if a pair $(l, r)$ is a funny pair, take $mid = \frac{l + r - 1}{2}$, then if $r - l + 1$ is an even number and $a_l \oplus a_{l+1} \oplus \ldots \oplus a_{mid} = a_{mid + 1} \oplus a_{mid + 2} \oplus \ldots \oplus a_r$, then the pair is funny. In other words, $\oplus$ of elements of the left half of the subarray from $l$ to $r$ should be equal to $\oplus$ of elements of the right half. Note that $\oplus$ denotes the bitwise XOR operation.

It is time to continue solving the contest, so Sasha asked you to solve this task.

萨沙喜欢编程。有一次，在一场非常漫长的竞赛中，萨沙觉得自己有点累了，需要放松一下，于是他决定休息片刻。但萨沙可不是普通人，他更喜欢以不寻常的方式放松——在闲暇时间里，他喜欢补题（upsolve）那些尚未解决的问题，因为补题非常有用。

因此，萨沙决定补做如下这道题：

你有一个包含 $n$ 个整数的数组 $a$。你需要统计“有趣的数对” $(l, r)$（其中 $l \leq r$）的个数。要判断一个数对 $(l, r)$ 是否为有趣的数对，请先计算 $mid = \frac{l + r - 1}{2}$；若子数组长度 $r - l + 1$ 为偶数，且左半部分 $a_l \oplus a_{l+1} \oplus \ldots \oplus a_{mid}$ 的异或值等于右半部分 $a_{mid + 1} \oplus a_{mid + 2} \oplus \ldots \oplus a_r$ 的异或值，则该数对是有趣的。换言之，子数组 $[l, r]$ 左半部分所有元素的异或值必须等于右半部分所有元素的异或值。注意：$\oplus$ 表示按位异或运算。

现在是时候继续投入竞赛了，因此萨沙请你来解决这个问题。

The first line contains one integer $n$ ($2 \le n \le 3 \cdot 10^5$) — the size of the array.

The second line contains $n$ integers $a_1, a_2, \ldots, a_n$ ($0 \le a_i \lt 2^{20}$) — array itself.

第一行包含一个整数 $n$（$2 \le n \le 3 \cdot 10^5$）—— 数组的大小。

第二行包含 $n$ 个整数 $a_1, a_2, \ldots, a_n$（$0 \le a_i \lt 2^{20}$）—— 数组本身。

Print one integer — the number of funny pairs. You should consider only pairs where $r - l + 1$ is even number.

输出一个整数——有趣的数对的数量。你只需考虑满足 $r - l + 1$ 为偶数的数对。

Be as cool as Sasha, upsolve problems!

In the first example, the only funny pair is $(2, 5)$, as $2 \oplus 3 = 4 \oplus 5 = 1$.

In the second example, funny pairs are $(2, 3)$, $(1, 4)$, and $(3, 6)$.

In the third example, there are no funny pairs.

像 Sasha 一样酷，把题目补做完！

在第一个样例中，唯一的“有趣对”是 $(2, 5)$，因为 $2 \oplus 3 = 4 \oplus 5 = 1$。

在第二个样例中，“有趣对”有 $(2, 3)$、$(1, 4)$ 和 $(3, 6)$。

在第三个样例中，不存在“有趣对”。