CF1601A.Array Elimination

You are given array $a_1, a_2, \ldots, a_n$ , consisting of non-negative integers.

Let's define operation of "elimination" with integer parameter $k$ ( $1 \leq k \leq n$ ) as follows:

• Choose $k$ distinct array indices $1 \leq i_1 < i_2 < \ldots < i_k \le n$ .
• Calculate $x = a_{i_1} ~ \& ~ a_{i_2} ~ \& ~ \ldots ~ \& ~ a_{i_k}$ , where $\&$ denotes the bitwise AND operation (notes section contains formal definition).
• Subtract $x$ from each of $a_{i_1}, a_{i_2}, \ldots, a_{i_k}$ ; all other elements remain untouched.

Find all possible values of $k$ , such that it's possible to make all elements of array $a$ equal to $0$ using a finite number of elimination operations with parameter $k$ . It can be proven that exists at least one possible $k$ for any array $a$ .

Note that you firstly choose $k$ and only after that perform elimination operations with value $k$ you've chosen initially.

Each test contains multiple test cases. The first line contains the number of test cases $t$ ( $1 \leq t \leq 10^4$ ). Description of the test cases follows.

The first line of each test case contains one integer $n$ ( $1 \leq n \leq 200\,000$ ) — the length of array $a$ .

The second line of each test case contains $n$ integers $a_1, a_2, \ldots, a_n$ ( $0 \leq a_i < 2^{30}$ ) — array $a$ itself.

It's guaranteed that the sum of $n$ over all test cases doesn't exceed $200\,000$ .

For each test case, print all values $k$ , such that it's possible to make all elements of $a$ equal to $0$ in a finite number of elimination operations with the given parameter $k$ .

Print them in increasing order.

In the first test case:

• If $k = 1$ , we can make four elimination operations with sets of indices $\{1\}$ , $\{2\}$ , $\{3\}$ , $\{4\}$ . Since $\&$ of one element is equal to the element itself, then for each operation $x = a_i$ , so $a_i - x = a_i - a_i = 0$ .
• If $k = 2$ , we can make two elimination operations with, for example, sets of indices $\{1, 3\}$ and $\{2, 4\}$ : $x = a_1 ~ \& ~ a_3$ $=$ $a_2 ~ \& ~ a_4$ $=$ $4 ~ \& ~ 4 = 4$ . For both operations $x = 4$ , so after the first operation $a_1 - x = 0$ and $a_3 - x = 0$ , and after the second operation — $a_2 - x = 0$ and $a_4 - x = 0$ .
• If $k = 3$ , it's impossible to make all $a_i$ equal to $0$ . After performing the first operation, we'll get three elements equal to $0$ and one equal to $4$ . After that, all elimination operations won't change anything, since at least one chosen element will always be equal to $0$ .
• If $k = 4$ , we can make one operation with set $\{1, 2, 3, 4\}$ , because $x = a_1 ~ \& ~ a_2 ~ \& ~ a_3 ~ \& ~ a_4$ $= 4$ .

In the second test case, if $k = 2$ then we can make the following elimination operations:

• Operation with indices $\{1, 3\}$ : $x = a_1 ~ \& ~ a_3$ $=$ $13 ~ \& ~ 25 = 9$ . $a_1 - x = 13 - 9 = 4$ and $a_3 - x = 25 - 9 = 16$ . Array $a$ will become equal to $[4, 7, 16, 19]$ .
• Operation with indices $\{3, 4\}$ : $x = a_3 ~ \& ~ a_4$ $=$ $16 ~ \& ~ 19 = 16$ . $a_3 - x = 16 - 16 = 0$ and $a_4 - x = 19 - 16 = 3$ . Array $a$ will become equal to $[4, 7, 0, 3]$ .
• Operation with indices $\{2, 4\}$ : $x = a_2 ~ \& ~ a_4$ $=$ $7 ~ \& ~ 3 = 3$ . $a_2 - x = 7 - 3 = 4$ and $a_4 - x = 3 - 3 = 0$ . Array $a$ will become equal to $[4, 4, 0, 0]$ .
• Operation with indices $\{1, 2\}$ : $x = a_1 ~ \& ~ a_2$ $=$ $4 ~ \& ~ 4 = 4$ . $a_1 - x = 4 - 4 = 0$ and $a_2 - x = 4 - 4 = 0$ . Array $a$ will become equal to $[0, 0, 0, 0]$ .

Formal definition of bitwise AND:

Let's define bitwise AND ( $\&$ ) as follows. Suppose we have two non-negative integers $x$ and $y$ , let's look at their binary representations (possibly, with leading zeroes): $x_k \dots x_2 x_1 x_0$ and $y_k \dots y_2 y_1 y_0$ . Here, $x_i$ is the $i$ -th bit of number $x$ , and $y_i$ is the $i$ -th bit of number $y$ . Let $r = x ~ \& ~ y$ is a result of operation $\&$ on number $x$ and $y$ . Then binary representation of $r$ will be $r_k \dots r_2 r_1 r_0$ , where:

$$ r_i = \begin{cases} 1, ~ \text{if} ~ x_i = 1 ~ \text{and} ~ y_i = 1 \\ 0, ~ \text{if} ~ x_i = 0 ~ \text{or} ~ y_i = 0 \end{cases} $$