题目描述
Fedya is a seasoned traveller and is planning his trip to Treeland. Treeland is a country with an ancient road system which is in the form of a tree structure. $N$ cities of Treeland are numbered by $N$ positive integers: $1,2,3,\ldots,N$.
Fedya has not yet decided the starting point (city) of his journey and the cities he will visit. But there are a few things you know about Fedya's trip:
Fedya is fond of travelling to great distances. So if he is currently located in city $\mbox{V}$, his destination will be a city which is most distant from city $\mbox{V}$.
There might be more than 1 such cities. In that case, Fedya will choose a city that was already visited as less times as possible in this journey.
There still might be more than 1 such cities. In that case, Fedya will go to the city with the smallest number.
Fedya has prepared a list of $\mbox{M}$ possible journeys. Each one is characterized by two integers - the starting city $\mbox{V}$ and the total number of cities to be visited, $\mbox{K}$. For each of them, he is keen to know the total distance travelled by him.
Input Format
The first line of input will contain two space separated integers $N$ and $\mbox{M}$ - the number of cities and the number of possible journeys.
Then, there will be $(N-1)$ lines, each of them will contain two space separated integers $\mbox{X}$ $\mathbf{Y}$, denoting the bi-directional road between the cities with numbers $\mbox{X}$ and $\mathbf{Y}$ with the unitary length.
Then there will be $\mbox{M}$ lines, each of them will have two space separated integers $\mbox{V}$ and $\mbox{K}$, denoting a journey.
Constraints
$1\leq N,M\leq10^5$
$1\leq V,X,Y\leq N$
$1\leq K\leq10^9$
Output Format
For each journey, output the travelled distance on a separate line.
Sample Input
8 7
2 1
3 2
4 2
5 1
6 1
7 1
8 7
4 6
3 4
6 3
7 6
4 6
7 1
2 6
Sample Output
24
16
11
23
24
3
23
Explanation
The tree in question is given in the picture below.
4 6 indicates that Fedya starts at 4. Now we see that the most distant city from 4 is 8. Fedya now travels to city 8. From 8, the most distance cities are [4, 3]. As 4 is already visited, he chooses to visit city 3. From city 3, he revisits city 8 and so on. The cities in the order of visit is 4 - > 8 -> 3 -> 8 -> 4 -> 8 -> 3 which sums to 24. Hence, the answer.
6 3 indicates that Fedya starts at city 6. From 6, the most distant cities are [3,4,8]. In this leg of the journey, no city is visited and hence Fedya chooses to visit the city with the smallest number 3. From 3, he visits 8 and then he ends his trip at city 4 which sums to 3 + 4 + 4 = 11. Hence, the answer.
输入格式
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输出格式
见题面