Buggy python submission (verdict: Runtime Error):
N = (int)(input())
edges = []
for _ in range(N-1):
    edges.append((list)(map(int, input().split())))

Q, K = (list)(map(int, input().split()))
querys = []
for _ in range(Q):
    querys.append((list)(map(int, input().split())))

'''
 N:num of nodes
 Q: num of query
 K: node must passed in query

'''
dist = [-1]*(N+1)
for e in edges:
    if dist[e[0]] == -1:
        dist[e[0]] = [[e[1], e[2]]]
    else:
        dist[e[0]].append([e[1], e[2]])

    if dist[e[1]] == -1:
        dist[e[1]] = [[e[0], e[2]]]
    else:
        dist[e[1]].append([e[0], e[2]])

dist_from_k = [-1]*(N+1)


def dfs(v, p, cost):
    if dist_from_k[v] != -1:
        return

    dist_from_k[v] = cost
    for e in dist[v]:
        if e[0] == p:
            continue
        dfs(e[0], v, cost+e[1])


dfs(K, -1, 0)

for q in querys:
    print(dist_from_k[q[0]] + dist_from_k[q[1]])


Fixed submission:
import sys
sys.setrecursionlimit(10**6)
N = (int)(input())
edges = []
for _ in range(N-1):
    edges.append((list)(map(int, input().split())))

Q, K = (list)(map(int, input().split()))
querys = []
for _ in range(Q):
    querys.append((list)(map(int, input().split())))

'''
 N:num of nodes
 Q: num of query
 K: node must passed in query

'''
dist = [-1]*(N+1)
for e in edges:
    if dist[e[0]] == -1:
        dist[e[0]] = [[e[1], e[2]]]
    else:
        dist[e[0]].append([e[1], e[2]])

    if dist[e[1]] == -1:
        dist[e[1]] = [[e[0], e[2]]]
    else:
        dist[e[1]].append([e[0], e[2]])

dist_from_k = [-1]*(N+1)


def dfs(v, cost):
    if dist_from_k[v] != -1:
        return

    dist_from_k[v] = cost
    for e in dist[v]:
        dfs(e[0], cost+e[1])


dfs(K, 0)

for q in querys:
    print(dist_from_k[q[0]] + dist_from_k[q[1]])

Buggy python submission (verdict: Runtime Error):
N = (int)(input())
edges = []
for _ in range(N-1):
    edges.append((list)(map(int, input().split())))

Q, K = (list)(map(int, input().split()))
querys = []
for _ in range(Q):
    querys.append((list)(map(int, input().split())))

'''
 N:num of nodes
 Q: num of query
 K: node must passed in query

'''
dist = [-1]*(N+1)
for e in edges:
    if dist[e[0]] == -1:
        dist[e[0]] = [[e[1], e[2]]]
    else:
        dist[e[0]].append([e[1], e[2]])

    if dist[e[1]] == -1:
        dist[e[1]] = [[e[0], e[2]]]
    else:
        dist[e[1]].append([e[0], e[2]])

dist_from_k = [-1]*(N+1)


def dfs(v, cost):
    if dist_from_k[v] != -1:
        return

    dist_from_k[v] = cost
    for e in dist[v]:
        dfs(e[0], cost+e[1])


dfs(K, 0)

for q in querys:
    print(dist_from_k[q[0]] + dist_from_k[q[1]])


Fixed submission:
import sys
sys.setrecursionlimit(10**6)
N = (int)(input())
edges = []
for _ in range(N-1):
    edges.append((list)(map(int, input().split())))

Q, K = (list)(map(int, input().split()))
querys = []
for _ in range(Q):
    querys.append((list)(map(int, input().split())))

'''
 N:num of nodes
 Q: num of query
 K: node must passed in query

'''
dist = [-1]*(N+1)
for e in edges:
    if dist[e[0]] == -1:
        dist[e[0]] = [[e[1], e[2]]]
    else:
        dist[e[0]].append([e[1], e[2]])

    if dist[e[1]] == -1:
        dist[e[1]] = [[e[0], e[2]]]
    else:
        dist[e[1]].append([e[0], e[2]])

dist_from_k = [-1]*(N+1)


def dfs(v, cost):
    if dist_from_k[v] != -1:
        return

    dist_from_k[v] = cost
    for e in dist[v]:
        dfs(e[0], cost+e[1])


dfs(K, 0)

for q in querys:
    print(dist_from_k[q[0]] + dist_from_k[q[1]])