Buggy python submission (verdict: Time Limit Exceeded):
import sys
sys.setrecursionlimit(1000000) 
N=int(input())
Branch=[[] for i in range(N)]
for i in range(N-1):
  a,b,c=map(int,input().split())
  Branch[a-1].append([b-1,c])
  Branch[b-1].append([a-1,c])
Q,K=map(int,input().split())
DistK=[float("Inf") for i in range(N)]
flag = [0 for i in range(N)]

def dfs(s,dist):
  DistK[s]=dist
  flag[s]=1
  
  for i in range(len(Branch[s])):
    if flag[Branch[s][i][0]]==0:
      dfs(Branch[s][i][0],dist+Branch[s][i][1])
      
  return 1
dfs(K-1,0)
for i in range(Q):
  x,y = map(int,input().split())
  print(DistK[x-1]+DistK[y-1])
  

Fixed submission:
import collections
N=int(input())
Branch=[[] for i in range(N)]
for i in range(N-1):
  a,b,c=map(int,input().split())
  Branch[a-1].append([b-1,c])
  Branch[b-1].append([a-1,c])
Q,K=map(int,input().split())
Dist=[float("Inf") for i in range(N)]
flag = [0 for i in range(N)]

que=collections.deque()
que.append(K-1)
Dist[K-1]=0
while len(que):
  u=que.pop()
  for i,j in Branch[u]:
    if Dist[i]==float("Inf"):
      Dist[i]=Dist[u]+j
      que.append(i)

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

Buggy python submission (verdict: Runtime Error):
N=int(input())
Branch=[[] for i in range(N)]
for i in range(N-1):
  a,b,c=map(int,input().split())
  Branch[a-1].append([b-1,c])
  Branch[b-1].append([a-1,c])
Q,K=map(int,input().split())
DistK=[float("Inf") for i in range(N)]
flag = [0 for i in range(N)]

def dfs(s,dist,flag,Branch,DistK):
  DistK[s]=dist
  flag[s]=1
  
  for i in range(len(Branch[s])):
    if flag[Branch[s][i][0]]==0:
      dfs(Branch[s][i][0],dist+Branch[s][i][1],flag,Branch,DistK)
      
  return 1
dfs(K-1,0,flag,Branch,DistK)
for i in range(Q):
  x,y = map(int,input().split())
  print(DistK[x-1]+DistK[y-1])
  

Fixed submission:
import collections
N=int(input())
Branch=[[] for i in range(N)]
for i in range(N-1):
  a,b,c=map(int,input().split())
  Branch[a-1].append([b-1,c])
  Branch[b-1].append([a-1,c])
Q,K=map(int,input().split())
Dist=[float("Inf") for i in range(N)]
flag = [0 for i in range(N)]

que=collections.deque()
que.append(K-1)
Dist[K-1]=0
while len(que):
  u=que.pop()
  for i,j in Branch[u]:
    if Dist[i]==float("Inf"):
      Dist[i]=Dist[u]+j
      que.append(i)

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

Buggy python submission (verdict: Runtime Error):
N=int(input())
Branch=[[] for i in range(N)]
for i in range(N-1):
  a,b,c=map(int,input().split())
  Branch[a-1].append([b-1,c])
  Branch[b-1].append([a-1,c])
Q,K=map(int,input().split())
DistK=[float("Inf") for i in range(N)]
flag = [0 for i in range(N)]

def dfs(s,dist):
  DistK[s]=dist
  flag[s]=1
  
  for i in range(len(Branch[s])):
    if flag[Branch[s][i][0]]==0:
      dfs(Branch[s][i][0],dist+Branch[s][i][1])
dfs(K-1,0)
      
for i in range(Q):
  x,y = map(int,input().split())
  print(DistK[x-1]+DistK[y-1])
  

Fixed submission:
import collections
N=int(input())
Branch=[[] for i in range(N)]
for i in range(N-1):
  a,b,c=map(int,input().split())
  Branch[a-1].append([b-1,c])
  Branch[b-1].append([a-1,c])
Q,K=map(int,input().split())
Dist=[float("Inf") for i in range(N)]
flag = [0 for i in range(N)]

que=collections.deque()
que.append(K-1)
Dist[K-1]=0
while len(que):
  u=que.pop()
  for i,j in Branch[u]:
    if Dist[i]==float("Inf"):
      Dist[i]=Dist[u]+j
      que.append(i)

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

Buggy python submission (verdict: Runtime Error):
N=int(input())
Branch=[[] for i in range(N)]
for i in range(N-1):
  a,b,c=map(int,input().split())
  Branch[a-1].append([b-1,c])
  Branch[b-1].append([a-1,c])
Q,K=map(int,input().split())
DistK=[float("Inf") for i in range(N)]
flag = [0 for i in range(N)]

def dfs(s,dist):
  DistK[s]=dist
  flag[s]=1
  
  for branch in Branch[s]:
    if flag[branch[0]]==0:
      dfs(branch[0],dist+branch[1])
dfs(K-1,0)
      
for i in range(Q):
  x,y = map(int,input().split())
  print(DistK[x-1]+DistK[y-1])
  

Fixed submission:
import collections
N=int(input())
Branch=[[] for i in range(N)]
for i in range(N-1):
  a,b,c=map(int,input().split())
  Branch[a-1].append([b-1,c])
  Branch[b-1].append([a-1,c])
Q,K=map(int,input().split())
Dist=[float("Inf") for i in range(N)]
flag = [0 for i in range(N)]

que=collections.deque()
que.append(K-1)
Dist[K-1]=0
while len(que):
  u=que.pop()
  for i,j in Branch[u]:
    if Dist[i]==float("Inf"):
      Dist[i]=Dist[u]+j
      que.append(i)

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