COCI '21 Contest 4 #4 Parkovi
View as PDFThe town administration has decided to embellish the landscape by building new parks. To make the parks not only look good, but also be useful, they need to carefully choose which neighbourhoods to build the parks in so that the kids from the other neighbourhoods have at least one park near them.
The town consists of  neighbourhoods connected by 
 roads of a certain
length. There is a unique path connecting each neighbourhood to any other
neighbourhood. In other words, the neighbourhoods and roads form a tree.
Exactly 
 parks should be built in different neighbourhoods so that the other
neighbourhoods have their nearest park as close to them as possible. To be
more precise, the administration wants to minimize the maximum distance from a neighbourhood to its
closest park.
Help the town administration determine which neighbourhoods should have a park built in them and determine the maximum distance from a neighbourhood to its closest park.
Input Specification
The first line contains two positive integers  and 
 
, the number of neighbourhoods
and the number of parks, respectively.
The  of the next 
 lines contains positive integers 
, 
, and 
 
,
which denotes that the neighbourhoods labeled 
 and 
 are connected by a road of length 
.
Output Specification
In the first line, print the least possible maximum distance from the problem statement.
In the second line, print  positive integers, the labels of the neighbourhoods which will have a park built
in them. If there is more than one solution, output any one.
Constraints
| Subtask | Points | Constraints | 
|---|---|---|
| 1 | 10 | |
| 2 | 10 | |
| 3 | 30 | |
| 4 | 60 | No additional constraints. | 
Sample Input 1
9 3
1 2 5
1 3 1
3 4 10
3 5 9
5 6 8
2 7 1
2 8 2
8 9 7
Sample Output 1
8
4 5 8
Sample Input 2
5 2
1 2 3
2 3 7
3 4 3
4 5 3
Sample Output 2
3
2 4
Sample Input 3
7 4
1 3 1
1 4 1
2 3 1
5 3 1
4 7 1
4 6 1
Sample Output 3
1
3 4 1 2
Explanation for Sample Output 3
If the parks were built only in neighbourhoods  and 
, the maximum distance wouldn't change, but the
city administration wants to build exactly 
 parks, so two more need to be built somewhere else.
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