Buggy python submission (verdict: Runtime Error):
from collections import deque
n = int(input())
e = [[] for _ in range(n)]
AB = [list(map(int, input().split())) for _ in range(n - 1)]
AB = [(a -1, b - 1) for a, b in AB]

for itr, (a, b) in enumerate(AB):
  e[a].append(b)
  e[b].append(b)
  
colors = [-1] * n

# ２色で塗分けする。
q = deque()
# 現在見ている頂点、親の色
q.append((0, 0))
while q:
  v, pcol = q.popleft()
  # 親と異なる色で塗る。
  if colors[v] == -1:
    col = not pcol
    colors[v] = col
  else:
    col = colors[v]
  for i in e[v]:
    if colors[i] == -1:
      q.append((i, col))

if -1 in colors:
  raise ValueError("error!")

m = [deque([i for i in range(1, n + 1) if i % 3 == j]) for j in range(3)]

# print(m)

def opop(n):
  if m[n]:
    p = m[n].pop()
  else:
    if n == 1 or n == 2:
      if m[0]:
        p = m[0].pop()
      else:
        p = m[3-n].pop()
    else:
      if m[1]:
        p = m[1].pop()
      else:
        p = m[2].pop()
  return p

ans = [0] * n

if sum(colors) <= n // 3:
  for itr, i in enumerate(colors):
    if i:
      ans[itr] = opop(0)
    else:
      ans[itr] = opop(1)
elif sum(colors) >= n - (n // 3) + 1:
  for itr, i in enumerate(colors):
    if not i:
      ans[itr] = opop(0)
    else:
      ans[itr] = opop(1)
else:
  for itr, i in enumerate(colors):
    if i:
      ans[itr] = opop(1)
    else:
      ans[itr] = opop(2)
print(*ans)

Fixed submission:
from collections import deque
n = int(input())
e = [[] for _ in range(n)]
AB = [list(map(int, input().split())) for _ in range(n - 1)]
AB = [(a -1, b - 1) for a, b in AB]

for itr, (a, b) in enumerate(AB):
  e[a].append(b)
  e[b].append(a)
  
colors = [-1] * n

# ２色で塗分けする。
q = deque()
# 現在見ている頂点、親の色
q.append((0, 0))
while q:
  v, pcol = q.popleft()
  # 親と異なる色で塗る。
  if colors[v] == -1:
    col = not pcol
    colors[v] = col
    for i in e[v]:
      if colors[i] == -1:
        q.append((i, col))

# print(e)
# print(colors)
        
m = [deque([i for i in range(1, n + 1) if i % 3 == j]) for j in range(3)]

# print(m)

def opop(n, ne):
  if m[n]:
    p = m[n].pop()
  else:
    if n == 1 or n == 2:
      if m[ne]:
        p = m[ne].pop()
      else:
        p = m[0].pop()
    else:
      if m[1]:
        p = m[1].pop()
      else:
        p = m[2].pop()
  return p

ans = [0] * n

if sum(colors) <= len(m[0]):
  for itr, i in enumerate(colors):
    if i:
      ans[itr] = opop(0, 0)
    else:
      ans[itr] = opop(1, 2)
elif sum(colors) >= len(m[1]) + len(m[2]):
  for itr, i in enumerate(colors):
    if not i:
      ans[itr] = opop(0, 0)
    else:
      ans[itr] = opop(1, 2)
else:
  for itr, i in enumerate(colors):
    if i:
      ans[itr] = opop(1, 0)
    else:
      ans[itr] = opop(2, 0)
print(*ans)

Buggy python submission (verdict: Runtime Error):
from collections import deque
n = int(input())
e = [[] for _ in range(n)]
AB = [list(map(int, input().split())) for _ in range(n - 1)]
AB = [(a -1, b - 1) for a, b in AB]

for itr, (a, b) in enumerate(AB):
  e[a].append(b)
  e[b].append(b)
  
colors = [-1] * n

# ２色で塗分けする。
q = deque()
# 現在見ている頂点、親の色
q.append((0, 0))
while q:
  v, pcol = q.popleft()
  # 親と異なる色で塗る。
  if colors[v] == -1:
    col = not pcol
    colors[v] = col
    for i in e[v]:
      if colors[i] == -1:
        q.append((i, col))

if -1 in colors:
  raise ValueError("error!")

m = [deque([i for i in range(1, n + 1) if i % 3 == j]) for j in range(3)]

# print(m)

def opop(n):
  if m[n]:
    p = m[n].pop()
  else:
    if n == 1 or n == 2:
      if m[0]:
        p = m[0].pop()
      else:
        p = m[3-n].pop()
    else:
      if m[1]:
        p = m[1].pop()
      else:
        p = m[2].pop()
  return p

ans = [0] * n

if sum(colors) <= n // 3:
  for itr, i in enumerate(colors):
    if i:
      ans[itr] = opop(0)
    else:
      ans[itr] = opop(1)
elif sum(colors) >= n - (n // 3) + 1:
  for itr, i in enumerate(colors):
    if not i:
      ans[itr] = opop(0)
    else:
      ans[itr] = opop(1)
else:
  for itr, i in enumerate(colors):
    if i:
      ans[itr] = opop(1)
    else:
      ans[itr] = opop(2)
print(*ans)

Fixed submission:
from collections import deque
n = int(input())
e = [[] for _ in range(n)]
AB = [list(map(int, input().split())) for _ in range(n - 1)]
AB = [(a -1, b - 1) for a, b in AB]

for itr, (a, b) in enumerate(AB):
  e[a].append(b)
  e[b].append(a)
  
colors = [-1] * n

# ２色で塗分けする。
q = deque()
# 現在見ている頂点、親の色
q.append((0, 0))
while q:
  v, pcol = q.popleft()
  # 親と異なる色で塗る。
  if colors[v] == -1:
    col = not pcol
    colors[v] = col
    for i in e[v]:
      if colors[i] == -1:
        q.append((i, col))

# print(e)
# print(colors)
        
m = [deque([i for i in range(1, n + 1) if i % 3 == j]) for j in range(3)]

# print(m)

def opop(n, ne):
  if m[n]:
    p = m[n].pop()
  else:
    if n == 1 or n == 2:
      if m[ne]:
        p = m[ne].pop()
      else:
        p = m[0].pop()
    else:
      if m[1]:
        p = m[1].pop()
      else:
        p = m[2].pop()
  return p

ans = [0] * n

if sum(colors) <= len(m[0]):
  for itr, i in enumerate(colors):
    if i:
      ans[itr] = opop(0, 0)
    else:
      ans[itr] = opop(1, 2)
elif sum(colors) >= len(m[1]) + len(m[2]):
  for itr, i in enumerate(colors):
    if not i:
      ans[itr] = opop(0, 0)
    else:
      ans[itr] = opop(1, 2)
else:
  for itr, i in enumerate(colors):
    if i:
      ans[itr] = opop(1, 0)
    else:
      ans[itr] = opop(2, 0)
print(*ans)

Buggy python submission (verdict: Runtime Error):
from collections import deque
n = int(input())
e = [[] for _ in range(n)]
AB = [list(map(int, input().split())) for _ in range(n - 1)]
AB = [(a -1, b - 1) for a, b in AB]

for itr, (a, b) in enumerate(AB):
  e[a].append(b)
  e[b].append(b)
  
colors = [-1] * n

# ２色で塗分けする。
q = deque()
# 現在見ている頂点、親の色
q.append((0, 0))
while q:
  v, pcol = q.popleft()
  # 親と異なる色で塗る。
  if colors[v] == -1:
    col = not pcol
    colors[v] = col
    for i in e[v]:
      if colors[i] == -1:
        q.append((i, col))

m = [deque([i for i in range(1, n + 1) if i % 3 == j]) for j in range(3)]

# print(m)

def opop(n):
  if n == 1 or n == 2:
    if m[n]:
      return m[n].pop()
    else:
      if m[0]:
        return m[0].pop()
      else:
        return m[3-n].pop()
  else:
    if m[n]:
      return m[n].pop()
    else:
      if m[1]:
        return m[1].pop()
      else:
        return m[2].pop()


ans = [0] * n

if sum(colors) < n // 3:
  for itr, i in enumerate(colors):
    if i:
      ans[itr] = opop(0)
    else:
      ans[itr] = opop(1)
if sum(colors) > n - (n // 3):
  for itr, i in enumerate(colors):
    if not i:
      ans[itr] = opop(0)
    else:
      ans[itr] = opop(1)
else:
  for itr, i in enumerate(colors):
    if i:
      ans[itr] = opop(1)
    else:
      ans[itr] = opop(2)
print(*ans)

Fixed submission:
from collections import deque
n = int(input())
e = [[] for _ in range(n)]
AB = [list(map(int, input().split())) for _ in range(n - 1)]
AB = [(a -1, b - 1) for a, b in AB]

for itr, (a, b) in enumerate(AB):
  e[a].append(b)
  e[b].append(a)
  
colors = [-1] * n

# ２色で塗分けする。
q = deque()
# 現在見ている頂点、親の色
q.append((0, 0))
while q:
  v, pcol = q.popleft()
  # 親と異なる色で塗る。
  if colors[v] == -1:
    col = not pcol
    colors[v] = col
    for i in e[v]:
      if colors[i] == -1:
        q.append((i, col))

# print(e)
# print(colors)
        
m = [deque([i for i in range(1, n + 1) if i % 3 == j]) for j in range(3)]

# print(m)

def opop(n, ne):
  if m[n]:
    p = m[n].pop()
  else:
    if n == 1 or n == 2:
      if m[ne]:
        p = m[ne].pop()
      else:
        p = m[0].pop()
    else:
      if m[1]:
        p = m[1].pop()
      else:
        p = m[2].pop()
  return p

ans = [0] * n

if sum(colors) <= len(m[0]):
  for itr, i in enumerate(colors):
    if i:
      ans[itr] = opop(0, 0)
    else:
      ans[itr] = opop(1, 2)
elif sum(colors) >= len(m[1]) + len(m[2]):
  for itr, i in enumerate(colors):
    if not i:
      ans[itr] = opop(0, 0)
    else:
      ans[itr] = opop(1, 2)
else:
  for itr, i in enumerate(colors):
    if i:
      ans[itr] = opop(1, 0)
    else:
      ans[itr] = opop(2, 0)
print(*ans)

Buggy python submission (verdict: Runtime Error):
from collections import deque
n = int(input())
e = [[] for _ in range(n)]
AB = [list(map(int, input().split())) for _ in range(n - 1)]
AB = [(a -1, b - 1) for a, b in AB]

for itr, (a, b) in enumerate(AB):
  e[a].append(b)
  e[b].append(b)
  
colors = [-1] * n

# ２色で塗分けする。
q = deque()
# 現在見ている頂点、親の色
q.append((0, 0))
while q:
  v, pcol = q.popleft()
  # 親と異なる色で塗る。
  if colors[v] == -1:
    col = not pcol
    colors[v] = col
    for i in e[v]:
      if colors[i] == -1:
        q.append((i, col))

m1 = deque([i for i in range(1, n + 1) if i % 3 == 1])
m2 = deque([i for i in range(1, n + 1) if i % 3 == 2])
m0 = deque([i for i in range(1, n + 1) if i % 3 == 0])

ans = [0] * n

if sum(colors) > n // 2:
  for itr, i in enumerate(colors):
    if i:
      if m1:
        ans[itr] = m1.pop()
      else:
        ans[itr] = m0.pop()
    else:
      if m2:
        ans[itr] = m2.pop()
      else:
        ans[itr] = m0.pop()
else:
  for itr, i in enumerate(colors):
    if not i:
      if m1:
        ans[itr] = m1.pop()
      else:
        ans[itr] = m0.pop()
    else:
      if m2:
        ans[itr] = m2.pop()
      else:
        ans[itr] = m0.pop()
print(*ans)

Fixed submission:
from collections import deque
n = int(input())
e = [[] for _ in range(n)]
AB = [list(map(int, input().split())) for _ in range(n - 1)]
AB = [(a -1, b - 1) for a, b in AB]

for itr, (a, b) in enumerate(AB):
  e[a].append(b)
  e[b].append(a)
  
colors = [-1] * n

# ２色で塗分けする。
q = deque()
# 現在見ている頂点、親の色
q.append((0, 0))
while q:
  v, pcol = q.popleft()
  # 親と異なる色で塗る。
  if colors[v] == -1:
    col = not pcol
    colors[v] = col
    for i in e[v]:
      if colors[i] == -1:
        q.append((i, col))

# print(e)
# print(colors)
        
m = [deque([i for i in range(1, n + 1) if i % 3 == j]) for j in range(3)]

# print(m)

def opop(n, ne):
  if m[n]:
    p = m[n].pop()
  else:
    if n == 1 or n == 2:
      if m[ne]:
        p = m[ne].pop()
      else:
        p = m[0].pop()
    else:
      if m[1]:
        p = m[1].pop()
      else:
        p = m[2].pop()
  return p

ans = [0] * n

if sum(colors) <= len(m[0]):
  for itr, i in enumerate(colors):
    if i:
      ans[itr] = opop(0, 0)
    else:
      ans[itr] = opop(1, 2)
elif sum(colors) >= len(m[1]) + len(m[2]):
  for itr, i in enumerate(colors):
    if not i:
      ans[itr] = opop(0, 0)
    else:
      ans[itr] = opop(1, 2)
else:
  for itr, i in enumerate(colors):
    if i:
      ans[itr] = opop(1, 0)
    else:
      ans[itr] = opop(2, 0)
print(*ans)

Buggy python submission (verdict: Runtime Error):
from collections import deque
n = int(input())
e = [[] for _ in range(n)]
AB = [list(map(int, input().split())) for _ in range(n - 1)]
AB = [(a -1, b - 1) for a, b in AB]

for itr, (a, b) in enumerate(AB):
  e[a].append(b)
  e[b].append(b)
  
colors = [-1] * n

# ２色で塗分けする。
q = deque()
# 現在見ている頂点、親の色
q.append((0, 0))
while q:
  v, pcol = q.popleft()
  # 親と異なる色で塗る。
  if colors[v] == -1:
    col = not pcol
    colors[v] = col
    for i in e[v]:
      if colors[i] == -1:
        q.append((i, col))

m1 = deque([i for i in range(1, n + 1) if i % 3 == 1])
m2 = deque([i for i in range(1, n + 1) if i % 3 == 2])
m0 = deque([i for i in range(1, n + 1) if i % 3 == 0])

ans = [0] * n

for itr, i in enumerate(colors):
  if i:
    if m1:
      ans[itr] = m1.pop()
    else:
      ans[itr] = m0.pop()
  else:
    if m2:
      ans[itr] = m2.pop()
    else:
      ans[itr] = m0.pop()

print(*ans)

Fixed submission:
from collections import deque
n = int(input())
e = [[] for _ in range(n)]
AB = [list(map(int, input().split())) for _ in range(n - 1)]
AB = [(a -1, b - 1) for a, b in AB]

for itr, (a, b) in enumerate(AB):
  e[a].append(b)
  e[b].append(a)
  
colors = [-1] * n

# ２色で塗分けする。
q = deque()
# 現在見ている頂点、親の色
q.append((0, 0))
while q:
  v, pcol = q.popleft()
  # 親と異なる色で塗る。
  if colors[v] == -1:
    col = not pcol
    colors[v] = col
    for i in e[v]:
      if colors[i] == -1:
        q.append((i, col))

# print(e)
# print(colors)
        
m = [deque([i for i in range(1, n + 1) if i % 3 == j]) for j in range(3)]

# print(m)

def opop(n, ne):
  if m[n]:
    p = m[n].pop()
  else:
    if n == 1 or n == 2:
      if m[ne]:
        p = m[ne].pop()
      else:
        p = m[0].pop()
    else:
      if m[1]:
        p = m[1].pop()
      else:
        p = m[2].pop()
  return p

ans = [0] * n

if sum(colors) <= len(m[0]):
  for itr, i in enumerate(colors):
    if i:
      ans[itr] = opop(0, 0)
    else:
      ans[itr] = opop(1, 2)
elif sum(colors) >= len(m[1]) + len(m[2]):
  for itr, i in enumerate(colors):
    if not i:
      ans[itr] = opop(0, 0)
    else:
      ans[itr] = opop(1, 2)
else:
  for itr, i in enumerate(colors):
    if i:
      ans[itr] = opop(1, 0)
    else:
      ans[itr] = opop(2, 0)
print(*ans)