Problem:
Score : 400 points

Problem Statement

You are given a tree with N vertices.

Here, a tree is a kind of graph, and more specifically, a connected undirected graph with N-1 edges, where N is the number of its vertices.

The i-th edge (1≤i≤N-1) connects Vertices a_i and b_i, and has a length of c_i.

You are also given Q queries and an integer K. In the j-th query (1≤j≤Q):

find the length of the shortest path from Vertex x_j and Vertex y_j via Vertex K.

Constraints

3≤N≤10^5

1≤a_i,b_i≤N (1≤i≤N-1)

1≤c_i≤10^9 (1≤i≤N-1)

The given graph is a tree.

1≤Q≤10^5

1≤K≤N

1≤x_j,y_j≤N (1≤j≤Q)

x_j≠y_j (1≤j≤Q)

x_j≠K,y_j≠K (1≤j≤Q)

Input

Input is given from Standard Input in the following format:

N
a_1 b_1 c_1
:
a_{N-1} b_{N-1} c_{N-1}
Q K
x_1 y_1
:
x_{Q} y_{Q}

Output

Print the responses to the queries in Q lines.

In the j-th line j(1≤j≤Q), print the response to the j-th query.

Sample Input 1

5
1 2 1
1 3 1
2 4 1
3 5 1
3 1
2 4
2 3
4 5

Sample Output 1

3
2
4

The shortest paths for the three queries are as follows:

Query 1: Vertex 2 → Vertex 1 → Vertex 2 → Vertex 4 : Length 1+1+1=3

Query 2: Vertex 2 → Vertex 1 → Vertex 3 : Length 1+1=2

Query 3: Vertex 4 → Vertex 2 → Vertex 1 → Vertex 3 → Vertex 5 : Length 1+1+1+1=4

Sample Input 2

7
1 2 1
1 3 3
1 4 5
1 5 7
1 6 9
1 7 11
3 2
1 3
4 5
6 7

Sample Output 2

5
14
22

The path for each query must pass Vertex K=2.

Sample Input 3

10
1 2 1000000000
2 3 1000000000
3 4 1000000000
4 5 1000000000
5 6 1000000000
6 7 1000000000
7 8 1000000000
8 9 1000000000
9 10 1000000000
1 1
9 10

Sample Output 3

17000000000

Solution in Ruby (2.7.1) (judge verdict: Time Limit Exceeded)

N=gets.to_i
nodes=(0..(N-1)).to_a
edges=[]
(N-1).times do
    a,b,c=gets.chomp.split(" ").map(&:to_i)
    edges.push([a-1,b-1,c])
    edges.push([b-1,a-1,c])
end
INF=10**15
def warshall_floyd(node_list, edge_list)
    d = Array.new(node_list.length) { Array.new(node_list.length,INF) }
    edge_list.each do |u, v, c|
        d[u][v] = c
    end
  
    node_list.each do |k|
        node_list.each do |i|
            node_list.each do |j|
                d[i][j] = [d[i][j], d[i][k] + d[k][j]].min
            end
        end
    end
    d
end
D=warshall_floyd(nodes,edges)

Q,K=gets.chomp.split(" ").map(&:to_i)
Q.times do
    x,y=gets.chomp.split(" ").map(&:to_i)
    puts D[x-1][K-1]+D[y-1][K-1]
end