Description

Input

The first line contains integer $n$ ($2 \le n \le 17$).

The $i$-th of the next $2^{n} - 3$ lines contains two integers $a_{i}$ and $b_{i}$ ($1 \le a_{i} \lt b_{i} \le 2^{n} - 2$) — meaning there is an edge between $a_{i}$ and $b_{i}$. It is guaranteed that the given edges form a tree.

Output

Print two lines.

In the first line, print a single integer — the number of answers. If given tree cannot be made by McDic's generation, then print $0$.

In the second line, print all possible answers in ascending order, separated by spaces. If the given tree cannot be made by McDic's generation, then don't print anything.

4
1 2
1 3
2 4
2 5
3 6
3 13
3 14
4 7
4 8
5 9
5 10
6 11
6 12

1
3

2
1 2

2
1 2

3
1 2
2 3
3 4
4 5
5 6

0

Note

In the first example, $3$ is the only possible answer.

In the second example, there are $2$ possible answers.

In the third example, the tree can't be generated by McDic's generation.