DMOPC '20 Contest 4 P6 - Petty Children
View as PDFDr. Henri is teaching a class of  young students. He knows that 
 of them are friends, but they have recently been divided by a controversial topic: does pineapple belong on pizza? For that reason, even if two children are friends, unless they agree on the controversial topic, they will not associate with each other and their friendship is broken.
To encourage friendships, Dr. Henri asks each of his  students to organize pairwise meetups among their friends. For example, if he asks a child with 
 friends to organize gatherings, the child could organize friend 
 to meet friend 
, but won't have anybody to pair friend 
 with.
Dr. Henri can subtly change the opinion of the children. He wants to find some way to organize the opinions of the children such that the maximum number of children can pair up their friends perfectly.
Constraints
No student will be friends with themselves, nor will any friendship be listed multiple times.
Subtask 1 [5%]
Subtask 2 [45%]
Subtask 3 [50%]
No additional constraints.
Input Specification
The first line contains  integers 
 and 
, the number of children and the number of friendships, respectively.
The next  lines each contain 
 integers 
 and 
, indicating that child 
 and 
 are friends.
Output Specification
On the first line, output , the maximum number of children that can pair up their friends perfectly.
On the next line, output  integers, the opinions of the 
 children. Each integer should be either 
, indicating that the 
 child prefers pineapple on pizza, or 
 indicating that the 
 child does not prefer pineapple on pizza.
If there are multiple configurations of opinions achieving , you may output any of them.
Note: your output must follow the standard convention of not having any leading or trailing whitespace, and it must end with a new line.
Sample Input
4 6
1 2
1 3
1 4
2 3
2 4
3 4
Sample Output
4
1 1 1 2
Explanation
Children , 
, and 
 each have 
 friends after being divided by the controversy. As such, they can pair each of their friends up perfectly.
For child number , they can pair up all of their 
 remaining friends perfectly.
Comments
Just like real life 😔