Buggy python submission (verdict: Time Limit Exceeded):
import sys
sys.setrecursionlimit(10 ** 6)

N = int(input())
E = [set() for _ in range(N)]
C = {}
for i in range(N-1):
  a,b,c = map(int,input().split())
  E[a-1].add(b-1)
  E[b-1].add(a-1)
  C[min(a-1,b-1)*N+max(a-1,b-1)] = c
  
Q,K = map(int,input().split())
K -= 1
Query = []
for i in range(Q):
  x,y = map(int,input().split())
  Query.append([x-1,y-1])
#print(E)
#print(C)
#print(K)
#print(Query)

Kcost = [0 for _ in range(N)]
def dfs(u,v):
  if v != -1:
    Kcost[u] = Kcost[v] + C[min(u,v)*N+max(u,v)]
  for t in E[u]:
    if t != K and Kcost[t] == 0:
      dfs(t,u)
dfs(K,-1)

for x,y in Query:
  print(Kcost[x]+Kcost[y])

Fixed submission:
import sys
sys.setrecursionlimit(10 ** 6)

N = int(input())
E = [set() for _ in range(N)]
C = {}
for i in range(N-1):
  a,b,c = map(int,input().split())
  E[a-1].add(b-1)
  E[b-1].add(a-1)
  C[min(a-1,b-1)*N+max(a-1,b-1)] = c
  
Q,K = map(int,input().split())
K -= 1
#print(E)
#print(C)
#print(K)

Kcost = [0 for _ in range(N)]
def dfs(u,v):
  if v != -1:
    Kcost[u] = Kcost[v] + C[min(u,v)*N+max(u,v)]
  for t in E[u]:
    if t != K and Kcost[t] == 0:
      dfs(t,u)
dfs(K,-1)

for i in range(Q):
  x,y = map(int,input().split())
  print(Kcost[x-1]+Kcost[y-1])

Buggy python submission (verdict: Runtime Error):
N = int(input())
E = [set() for _ in range(N)]
C = {}
for i in range(N-1):
  a,b,c = map(int,input().split())
  E[a-1].add(b-1)
  E[b-1].add(a-1)
  C[min(a-1,b-1)*N+max(a-1,b-1)] = c
  
Q,K = map(int,input().split())
K -= 1
Query = []
for i in range(Q):
  x,y = map(int,input().split())
  Query.append([x-1,y-1])
#print(E)
#print(C)
#print(K)
#print(Query)

Kcost = [0 for _ in range(N)]
def dfs(u,v):
  if v != -1:
    Kcost[u] = Kcost[v] + C[min(u,v)*N+max(u,v)]
  for t in E[u]:
    if t != K and Kcost[t] == 0:
      dfs(t,u)
dfs(K,-1)

for x,y in Query:
  print(Kcost[x]+Kcost[y])

Fixed submission:
import sys
sys.setrecursionlimit(10 ** 6)

N = int(input())
E = [set() for _ in range(N)]
C = {}
for i in range(N-1):
  a,b,c = map(int,input().split())
  E[a-1].add(b-1)
  E[b-1].add(a-1)
  C[min(a-1,b-1)*N+max(a-1,b-1)] = c
  
Q,K = map(int,input().split())
K -= 1
#print(E)
#print(C)
#print(K)

Kcost = [0 for _ in range(N)]
def dfs(u,v):
  if v != -1:
    Kcost[u] = Kcost[v] + C[min(u,v)*N+max(u,v)]
  for t in E[u]:
    if t != K and Kcost[t] == 0:
      dfs(t,u)
dfs(K,-1)

for i in range(Q):
  x,y = map(int,input().split())
  print(Kcost[x-1]+Kcost[y-1])

Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
E = [set() for _ in range(N)]
C = [[0 for _ in range(N)] for _ in range(N)]
for i in range(N-1):
  a,b,c = map(int,input().split())
  E[a-1].add(b-1)
  E[b-1].add(a-1)
  C[a-1][b-1] = c
  C[b-1][a-1] = c
Q,K = map(int,input().split())
K -= 1
Query = []
for i in range(Q):
  x,y = map(int,input().split())
  Query.append([x-1,y-1])
#print(E)
#print(C)
#print(K)
#print(Query)

Kcost = [0 for _ in range(N)]
def dfs(u,v):
  if v != -1:
    Kcost[u] = Kcost[v] + C[u][v]
  for t in E[u]:
    if t != K and Kcost[t] == 0:
      dfs(t,u)
dfs(K,-1)

for x,y in Query:
  print(Kcost[x]+Kcost[y])

Fixed submission:
import sys
sys.setrecursionlimit(10 ** 6)

N = int(input())
E = [set() for _ in range(N)]
C = {}
for i in range(N-1):
  a,b,c = map(int,input().split())
  E[a-1].add(b-1)
  E[b-1].add(a-1)
  C[min(a-1,b-1)*N+max(a-1,b-1)] = c
  
Q,K = map(int,input().split())
K -= 1
#print(E)
#print(C)
#print(K)

Kcost = [0 for _ in range(N)]
def dfs(u,v):
  if v != -1:
    Kcost[u] = Kcost[v] + C[min(u,v)*N+max(u,v)]
  for t in E[u]:
    if t != K and Kcost[t] == 0:
      dfs(t,u)
dfs(K,-1)

for i in range(Q):
  x,y = map(int,input().split())
  print(Kcost[x-1]+Kcost[y-1])