Define the binary encoding of a finite set of natural numbers $T \subseteq \{0,1,2,\ldots\}$ as $f(T) = \sum\limits_{i \in T} 2^i$. For example, $f(\{0,2\}) = 2^0 + 2^2 = 5$ and $f(\{\}) = 0$. Notice that $f$ is a bijection from all such sets to all non-negative integers. As such, $f^{-1}$ is also defined.

You are given an integer $n$ along with $2^n-1$ sets $V_1,V_2,\ldots,V_{2^n-1}$.

Find all sets $S$ that satisfy the following constraint:

• $S \subseteq \{0,1,\ldots,n-1\}$. Note that $S$ can be empty.
• For all non-empty subsets $T \subseteq \{0,1,\ldots,n-1\}$, $|S \cap T| \in V_{f(T)}$.

Due to the large input and output, both input and output will be given in terms of binary encodings of the sets.

Input

The first line of input contains a single integer $n$ ($1 \leq n \leq 20$).

The second line of input contains $2^n-1$ integers $v_1,v_2,\ldots,v_{2^n-1}$ ($0 \leq v_i \lt 2^{n+1}$) — the sets $V_i$ given in their binary encoding where $V_i = f^{-1}(v_i)$.

Output

The first line of output should contain an integer $k$ indicating the number of possible $S$.

In the following $k$ lines, you should output $f(S)$ for all possible $S$ in increasing order.

Note

In the first test case, one possible $S$ is $f^{-1}(3) = \{0,1\}$. All the non-empty subsets $T \subseteq \{0,1,2\}$ and the corresponding $|S \cap T|$, $f(T)$ and $V_f(T)$ are as follows:

$T$$|S\cap T|$$f(T)$$V_{f(T)}$$\{0\}$$1$$1$$\{0,1,2,3\}$$\{1\}$$1$$2$$\{0,1,2,3\}$$\{2\}$$0$$4$$\{0,1,2,3\}$$\{0,1\}$$2$$3$$\{0,1,2,3\}$$\{0,2\}$$1$$5$$\{0,1,2,3\}$$\{1,2\}$$1$$6$$\{0,1,2,3\}$$\{0,1,2\}$$2$$7$$\{2,3\}$