Given a graph with n vertices (2 <= n <= 200). Find the largest set of vetices that each two vertices are connected.

Time: 1s, memory: 256GB

Input: First line contains two numbers n and k — the vertices and the edges.

Next k lines contains the k edges.

Output: The first line contain one number — The size of the set

The second line represents the vertices in the set. If there are more than one set that have the maximum size, print the set that is lexicographically smallest.

Example:

Input:

5 3

1 3

1 4

2 5

Output:

2

1 4

How can I solve this problem? Can you help me with this? Thank you!