Buggy python submission (verdict: Time Limit Exceeded):
import queue

N = int(input())
tree = [[] for _ in range(N)]

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

Q, K = map(int, input().split())
K -= 1

depth = [0 for _ in range(N)]

def bfs(v, p = -1, d = 0):
    q = queue.Queue()
    q.put([v, p, d])
    while not q.empty():
        cur = q.get()
        depth[cur[0]] = cur[2]
        for i, j in tree[cur[0]]:
            if i == cur[1]:
                continue
            q.put([i, cur[0], cur[2] + j])

bfs(K)

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

Fixed submission:
N = int(input())
tree = [[] for _ in range(N)]

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

Q, K = map(int, input().split())
K -= 1

depth = [0 for _ in range(N)]

def dfs(v, p = -1, d = 0):
    St = []
    St.append([v, p, d])
    # 空のシーケンスは偽になる
    while St:
        cur = St.pop()
        depth[cur[0]] = cur[2]
        for i, j in tree[cur[0]]:
            if i == cur[1]:
                continue
            St.append([i, cur[0], cur[2] + j])

dfs(K)

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

Buggy python submission (verdict: Runtime Error):

N = int(input())
tree = [[] for _ in range(N)]

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

Q, K = map(int, input().split())
K -= 1

depth = [0 for _ in range(N)]

def dfs(v, p = -1, d = 0):
    depth[v] = d
    for i, j in tree[v]:
        if i == p:
            continue
        dfs(i, v, d + j)

dfs(K)

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

Fixed submission:
N = int(input())
tree = [[] for _ in range(N)]

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

Q, K = map(int, input().split())
K -= 1

depth = [0 for _ in range(N)]

def dfs(v, p = -1, d = 0):
    St = []
    St.append([v, p, d])
    # 空のシーケンスは偽になる
    while St:
        cur = St.pop()
        depth[cur[0]] = cur[2]
        for i, j in tree[cur[0]]:
            if i == cur[1]:
                continue
            St.append([i, cur[0], cur[2] + j])

dfs(K)

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

Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
M = N-1
inf = float("inf")
dp = [[inf]*N for _ in [0]*N]
for i in range(N):dp[i][i] = 0
q = [list(map(int, input().split())) for i in range(M)]
Q , K = map(int, input().split())
p = [list(map(int, input().split())) for i in range(Q)]
ans = 0
 
for a,b,c in q:
    dp[a-1][b-1] = c
    dp[b-1][a-1] = c
for k in range(N):
    for i in range(N):
        for j in range(N):
            dp[i][j] = min(dp[i][j],dp[i][k]+dp[k][j])
for a,b in p:
    print(dp[a-1][K-1]+dp[K-1][b-1])



Fixed submission:
N = int(input())
tree = [[] for _ in range(N)]

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

Q, K = map(int, input().split())
K -= 1

depth = [0 for _ in range(N)]

def dfs(v, p = -1, d = 0):
    St = []
    St.append([v, p, d])
    # 空のシーケンスは偽になる
    while St:
        cur = St.pop()
        depth[cur[0]] = cur[2]
        for i, j in tree[cur[0]]:
            if i == cur[1]:
                continue
            St.append([i, cur[0], cur[2] + j])

dfs(K)

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