Buggy python submission (verdict: Runtime Error):
import sys
sys.setrecursionlimit(50000)

N = int(input())
M = [[] for i in range(N+1)]

for i in range(N-1):
    a, b, c = list(map(int, input().split(" ")))
    M[a].append((b,c))
    M[b].append((a,c))

Qn, K = list(map(int, input().split(" ")))

Q = []
for i in range(Qn):
    Q.append(list(map(int, input().split(" "))))

distance = [0]*(N+1)

def dfs(k, parent, dist):
    for n, x in M[k]:
        if n != parent:
            distance[n] = dist + x
            dfs(n, k, dist + x)

dfs(K, 0, 0)
for q in Q:
    print(distance[q[0]] + distance[q[1]])


Fixed submission:
import sys
sys.setrecursionlimit(1000000)

N = int(input())
M = [[] for i in range(N+1)]

for i in range(N-1):
    a, b, c = list(map(int, input().split(" ")))
    M[a].append((b,c))
    M[b].append((a,c))

Qn, K = list(map(int, input().split(" ")))

Q = []
for i in range(Qn):
    Q.append(list(map(int, input().split(" "))))

distance = [0]*(N+1)

def dfs(k, parent, dist):
    for n, x in M[k]:
        if n != parent:
            distance[n] = dist + x
            dfs(n, k, dist + x)

dfs(K, 0, 0)
for q in Q:
    print(distance[q[0]] + distance[q[1]])

Buggy python submission (verdict: Runtime Error):
N = int(input())
M = [[] for i in range(N+1)]

for i in range(N-1):
    a, b, c = list(map(int, input().split(" ")))
    M[a].append((b,c))
    M[b].append((a,c))

Qn, K = list(map(int, input().split(" ")))

Q = []
for i in range(Qn):
    Q.append(list(map(int, input().split(" "))))

distance = [0]*(N+1)

def dfs(k, parent, dist):
    for n, x in M[k]:
        if n != parent:
            distance[n] = dist + x
            dfs(n, k, dist + x)

dfs(K, 0, 0)
for q in Q:
    print(distance[q[0]] + distance[q[1]])


Fixed submission:
import sys
sys.setrecursionlimit(1000000)

N = int(input())
M = [[] for i in range(N+1)]

for i in range(N-1):
    a, b, c = list(map(int, input().split(" ")))
    M[a].append((b,c))
    M[b].append((a,c))

Qn, K = list(map(int, input().split(" ")))

Q = []
for i in range(Qn):
    Q.append(list(map(int, input().split(" "))))

distance = [0]*(N+1)

def dfs(k, parent, dist):
    for n, x in M[k]:
        if n != parent:
            distance[n] = dist + x
            dfs(n, k, dist + x)

dfs(K, 0, 0)
for q in Q:
    print(distance[q[0]] + distance[q[1]])

Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
M = [[0 for col in range(N)] for row in range(N)]

for i in range(N-1):
    a, b, c = list(map(int, input().split(" ")))
    M[a-1][b-1] = M[b-1][a-1] = c

Qn, K = list(map(int, input().split(" ")))

Q = []
for i in range(Qn):
    Q.append(list(map(int, input().split(" "))))

distance = [0]*N

def dfs(k, graph, dist):
    result = {}
    for n in range(N):
        x = graph[k][n]
        if x != 0:
            distance[n] = dist + x
            graph[n][k] = 0
            dfs(n, graph, dist + x)

dfs(K-1, M, 0)

for q in Q:
    print(distance[q[0]-1] + distance[q[1]-1])


Fixed submission:
import sys
sys.setrecursionlimit(1000000)

N = int(input())
M = [[] for i in range(N+1)]

for i in range(N-1):
    a, b, c = list(map(int, input().split(" ")))
    M[a].append((b,c))
    M[b].append((a,c))

Qn, K = list(map(int, input().split(" ")))

Q = []
for i in range(Qn):
    Q.append(list(map(int, input().split(" "))))

distance = [0]*(N+1)

def dfs(k, parent, dist):
    for n, x in M[k]:
        if n != parent:
            distance[n] = dist + x
            dfs(n, k, dist + x)

dfs(K, 0, 0)
for q in Q:
    print(distance[q[0]] + distance[q[1]])

Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
M = [[0 for col in range(N)] for row in range(N)]

for i in range(N-1):
    a, b, c = list(map(int, input().split(" ")))
    M[a-1][b-1] = M[b-1][a-1] = c

Qn, K = list(map(int, input().split(" ")))

Q = []
for i in range(Qn):
    Q.append(list(map(int, input().split(" "))))

def dfs(k, graph, dist):
    result = {}
    for n in range(N):
        x = graph[k][n]
        if x != 0:
            result[n] = dist + x
            graph[n][k] = 0
            result.update(dfs(n, graph, dist + x))
    return result

result = dfs(K-1, M, 0)

for q in Q:
    print(result[q[0]-1] + result[q[1]-1])


Fixed submission:
import sys
sys.setrecursionlimit(1000000)

N = int(input())
M = [[] for i in range(N+1)]

for i in range(N-1):
    a, b, c = list(map(int, input().split(" ")))
    M[a].append((b,c))
    M[b].append((a,c))

Qn, K = list(map(int, input().split(" ")))

Q = []
for i in range(Qn):
    Q.append(list(map(int, input().split(" "))))

distance = [0]*(N+1)

def dfs(k, parent, dist):
    for n, x in M[k]:
        if n != parent:
            distance[n] = dist + x
            dfs(n, k, dist + x)

dfs(K, 0, 0)
for q in Q:
    print(distance[q[0]] + distance[q[1]])