Buggy python submission (verdict: Runtime Error):
from sys import stdin, setrecursionlimit
from collections import deque

setrecursionlimit(10 ** 9)

N = int(stdin.readline())
ab = [list(map(int, stdin.readline().split())) for i in range(N - 1)]

# 1 index
graph = [[] for i in range(N + 1)]

for a, b in ab:
    graph[a].append(b)
    graph[b].append(a)

q = deque([])

mod0 = deque([])
mod1 = deque([])
mod2 = deque([])

for k in range(1, N + 1):
    if k % 3 == 0:
        mod0.append(k)
    elif k % 3 == 1:
        mod1.append(k)
    else:
        mod2.append(k)

dist = [-1] * (N + 1)


def bfs(start):
    q.append(start)
    dist[start] = 0

    while q:
        now = q.popleft()

        for node in graph[now]:
            if dist[node] != -1:
                continue
            else:
                dist[node] = dist[now] + 1
                q.append(node)


node_p = [0] * (N + 1)


def modfit(i):
    if even <= N / 3:
        if dist[i] % 2 == 0:
            node_p[i] = mod0.pop()

        else:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    elif odd <= N / 3:
        if dist[i] % 2 != 0:
            node_p[i] = mod0.pop()

        else:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    else:
        if dist[i] % 2 == 0:
            if mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()
        else:
            if mod1:
                node_p[i] = mod1.pop()
            else:
                node_p[i] = mod0.pop()

    print(node_p[i], end=" ")


odd = 0
even = 0

bfs(1)

for d in dist:
    if d % 2 == 0:
        even += 1
    else:
        odd += 1

for k in range(1, N + 1):
    modfit(k)

print()


Fixed submission:
from sys import stdin, setrecursionlimit
from collections import deque

setrecursionlimit(10 ** 9)

N = int(stdin.readline())
ab = [list(map(int, stdin.readline().split())) for i in range(N - 1)]

# 1 index
graph = [[] for i in range(N + 1)]

for a, b in ab:
    graph[a].append(b)
    graph[b].append(a)

q = deque([])

mod0 = deque([])
mod1 = deque([])
mod2 = deque([])

for k in range(1, N + 1):
    if k % 3 == 0:
        mod0.append(k)
    elif k % 3 == 1:
        mod1.append(k)
    else:
        mod2.append(k)

dist = [-1] * (N + 1)


def bfs(start):
    q.append(start)
    dist[start] = 0

    while q:
        now = q.popleft()

        for node in graph[now]:
            if dist[node] != -1:
                continue
            else:
                dist[node] = dist[now] + 1
                q.append(node)


node_p = [0] * (N + 1)


def modfit(i):
    if even <= N / 3:
        if dist[i] % 2 == 0:
            node_p[i] = mod0.pop()

        else:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    elif odd <= N / 3:
        if dist[i] % 2 != 0:
            node_p[i] = mod0.pop()

        else:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    else:
        if dist[i] % 2 == 0:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod0:
                node_p[i] = mod0.pop()
            else:
                print(-1)
                exit(0)
        else:
            if mod2:
                node_p[i] = mod2.pop()
            elif mod0:
                node_p[i] = mod0.pop()
            else:
                print(-1)
                exit(0)

    print(node_p[i], end=" ")


odd = 0
even = 0

bfs(N)

for i in range (1,N + 1):
    if dist[i] % 2 == 0:
        even += 1
    else:
        odd += 1

for k in range(1, N + 1):
    modfit(k)

print()

Buggy python submission (verdict: Runtime Error):
from sys import stdin, setrecursionlimit
from collections import deque

setrecursionlimit(10 ** 9)

N = int(stdin.readline())
ab = [list(map(int, stdin.readline().split())) for i in range(N - 1)]

# 1 index
graph = [[] for i in range(N + 1)]

for a, b in ab:
    graph[a].append(b)
    graph[b].append(a)

q = deque([])

mod0 = deque([])
mod1 = deque([])
mod2 = deque([])

for k in range(1, N + 1):
    if k % 3 == 0:
        mod0.append(k)
    elif k % 3 == 1:
        mod1.append(k)
    else:
        mod2.append(k)

dist = [-1] * (N + 1)


def bfs(start):
    q.append(start)
    dist[start] = 0

    while q:
        now = q.popleft()

        for node in graph[now]:
            if dist[node] != -1:
                continue
            else:
                dist[node] = dist[now] + 1
                q.append(node)


node_p = [0] * (N + 1)


def modfit(i):
    if even <= N // 3:
        if dist[i] % 2 == 0:
            node_p[i] = mod0.pop()

        else:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    elif odd <= N // 3:
        if dist[i] % 2 != 0:
            node_p[i] = mod0.pop()

        else:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    else:
        if dist[i] % 2 == 0:
            if mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()
        else:
            if mod1:
                node_p[i] = mod1.pop()
            else:
                node_p[i] = mod0.pop()

    print(node_p[i], end=" ")


odd = 0
even = 0

bfs(1)

for d in dist:
    if d % 2 == 0:
        even += 1
    else:
        odd += 1

for k in range(1, N + 1):
    modfit(k)

print()


Fixed submission:
from sys import stdin, setrecursionlimit
from collections import deque

setrecursionlimit(10 ** 9)

N = int(stdin.readline())
ab = [list(map(int, stdin.readline().split())) for i in range(N - 1)]

# 1 index
graph = [[] for i in range(N + 1)]

for a, b in ab:
    graph[a].append(b)
    graph[b].append(a)

q = deque([])

mod0 = deque([])
mod1 = deque([])
mod2 = deque([])

for k in range(1, N + 1):
    if k % 3 == 0:
        mod0.append(k)
    elif k % 3 == 1:
        mod1.append(k)
    else:
        mod2.append(k)

dist = [-1] * (N + 1)


def bfs(start):
    q.append(start)
    dist[start] = 0

    while q:
        now = q.popleft()

        for node in graph[now]:
            if dist[node] != -1:
                continue
            else:
                dist[node] = dist[now] + 1
                q.append(node)


node_p = [0] * (N + 1)


def modfit(i):
    if even <= N / 3:
        if dist[i] % 2 == 0:
            node_p[i] = mod0.pop()

        else:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    elif odd <= N / 3:
        if dist[i] % 2 != 0:
            node_p[i] = mod0.pop()

        else:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    else:
        if dist[i] % 2 == 0:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod0:
                node_p[i] = mod0.pop()
            else:
                print(-1)
                exit(0)
        else:
            if mod2:
                node_p[i] = mod2.pop()
            elif mod0:
                node_p[i] = mod0.pop()
            else:
                print(-1)
                exit(0)

    print(node_p[i], end=" ")


odd = 0
even = 0

bfs(N)

for i in range (1,N + 1):
    if dist[i] % 2 == 0:
        even += 1
    else:
        odd += 1

for k in range(1, N + 1):
    modfit(k)

print()

Buggy python submission (verdict: Runtime Error):
from sys import stdin, setrecursionlimit
from collections import deque

setrecursionlimit(10 ** 9)

N = int(stdin.readline())
ab = [list(map(int, stdin.readline().split())) for i in range(N - 1)]

# 1 index
graph = [[] for i in range(N + 1)]

for a, b in ab:
    graph[a].append(b)
    graph[b].append(a)

q = deque([])

mod0 = deque([])
mod1 = deque([])
mod2 = deque([])

for i in range(1, N + 1):
    if i % 3 == 0:
        mod0.append(i)
    elif i % 3 == 1:
        mod1.append(i)
    else:
        mod2.append(i)

dist = [-1] * (N + 1)


def bfs(start):
    q.append(start)
    dist[start] = 0

    while q:
        now = q.popleft()

        for node in graph[now]:
            if dist[node] != -1:
                continue
            else:
                dist[node] = dist[now] + 1
                q.append(node)


node_p = [0] * (N + 1)


def modfit(i):
    if even < N // 3:
        if dist[i] % 2 == 0:
            node_p[i] = mod0.pop()

        else:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    elif odd < N // 3:
        if dist[i] % 2 != 0:
            node_p[i] = mod0.pop()

        else:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    else:
        if dist[i] % 2 == 0:
            if mod1:
                node_p[i] = mod1.pop()
            else:
                node_p[i] = mod0.pop()
        else:
            if mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    print(node_p[i], end=" ")


odd = 0
even = 0

bfs(1)

for d in dist:
    if d % 2 == 0:
        even += 1
    else:
        odd += 1

for i in range(1, N + 1):
    modfit(i)

print()


Fixed submission:
from sys import stdin, setrecursionlimit
from collections import deque

setrecursionlimit(10 ** 9)

N = int(stdin.readline())
ab = [list(map(int, stdin.readline().split())) for i in range(N - 1)]

# 1 index
graph = [[] for i in range(N + 1)]

for a, b in ab:
    graph[a].append(b)
    graph[b].append(a)

q = deque([])

mod0 = deque([])
mod1 = deque([])
mod2 = deque([])

for k in range(1, N + 1):
    if k % 3 == 0:
        mod0.append(k)
    elif k % 3 == 1:
        mod1.append(k)
    else:
        mod2.append(k)

dist = [-1] * (N + 1)


def bfs(start):
    q.append(start)
    dist[start] = 0

    while q:
        now = q.popleft()

        for node in graph[now]:
            if dist[node] != -1:
                continue
            else:
                dist[node] = dist[now] + 1
                q.append(node)


node_p = [0] * (N + 1)


def modfit(i):
    if even <= N / 3:
        if dist[i] % 2 == 0:
            node_p[i] = mod0.pop()

        else:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    elif odd <= N / 3:
        if dist[i] % 2 != 0:
            node_p[i] = mod0.pop()

        else:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    else:
        if dist[i] % 2 == 0:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod0:
                node_p[i] = mod0.pop()
            else:
                print(-1)
                exit(0)
        else:
            if mod2:
                node_p[i] = mod2.pop()
            elif mod0:
                node_p[i] = mod0.pop()
            else:
                print(-1)
                exit(0)

    print(node_p[i], end=" ")


odd = 0
even = 0

bfs(N)

for i in range (1,N + 1):
    if dist[i] % 2 == 0:
        even += 1
    else:
        odd += 1

for k in range(1, N + 1):
    modfit(k)

print()

Buggy python submission (verdict: Runtime Error):
from sys import stdin, setrecursionlimit
from collections import deque

setrecursionlimit(10 ** 9)

N = int(stdin.readline())
ab = [list(map(int, stdin.readline().split())) for i in range(N - 1)]

# 1 index
graph = [[] for i in range(N + 1)]

for a, b in ab:
    graph[a].append(b)
    graph[b].append(a)

q = deque([])

mod0 = deque([])
mod1 = deque([])
mod2 = deque([])

for i in range(1, N + 1):
    if i % 3 == 0:
        mod0.append(i)
    elif i % 3 == 1:
        mod1.append(i)
    else:
        mod2.append(i)

dist = [-1] * (N + 1)


def bfs(start):
    q.append(start)
    dist[start] = 0

    while q:
        now = q.popleft()

        for node in graph[now]:
            if dist[node] != -1:
                continue
            else:
                dist[node] = dist[now] + 1
                q.append(node)


node_p = [0] * (N + 1)


def modfit(i):
    if even < N / 3:
        if dist[i] % 2 == 0:
            node_p[i] = mod0.pop()

        else:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    elif odd < N / 3:
        if dist[i] % 2 != 0:
            node_p[i] = mod0.pop()

        else:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    else:
        if dist[i] % 2 == 0:
            if mod1:
                node_p[i] = mod1.pop()
            else:
                node_p[i] = mod0.pop()
        else:
            if mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    print(node_p[i], end=" ")


odd = 0
even = 0

bfs(1)

for d in dist:
    if d % 2 == 0:
        even += 1
    else:
        odd += 1

for i in range(1, N + 1):
    modfit(i)

print()


Fixed submission:
from sys import stdin, setrecursionlimit
from collections import deque

setrecursionlimit(10 ** 9)

N = int(stdin.readline())
ab = [list(map(int, stdin.readline().split())) for i in range(N - 1)]

# 1 index
graph = [[] for i in range(N + 1)]

for a, b in ab:
    graph[a].append(b)
    graph[b].append(a)

q = deque([])

mod0 = deque([])
mod1 = deque([])
mod2 = deque([])

for k in range(1, N + 1):
    if k % 3 == 0:
        mod0.append(k)
    elif k % 3 == 1:
        mod1.append(k)
    else:
        mod2.append(k)

dist = [-1] * (N + 1)


def bfs(start):
    q.append(start)
    dist[start] = 0

    while q:
        now = q.popleft()

        for node in graph[now]:
            if dist[node] != -1:
                continue
            else:
                dist[node] = dist[now] + 1
                q.append(node)


node_p = [0] * (N + 1)


def modfit(i):
    if even <= N / 3:
        if dist[i] % 2 == 0:
            node_p[i] = mod0.pop()

        else:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    elif odd <= N / 3:
        if dist[i] % 2 != 0:
            node_p[i] = mod0.pop()

        else:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    else:
        if dist[i] % 2 == 0:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod0:
                node_p[i] = mod0.pop()
            else:
                print(-1)
                exit(0)
        else:
            if mod2:
                node_p[i] = mod2.pop()
            elif mod0:
                node_p[i] = mod0.pop()
            else:
                print(-1)
                exit(0)

    print(node_p[i], end=" ")


odd = 0
even = 0

bfs(N)

for i in range (1,N + 1):
    if dist[i] % 2 == 0:
        even += 1
    else:
        odd += 1

for k in range(1, N + 1):
    modfit(k)

print()

Buggy python submission (verdict: Runtime Error):
from sys import setrecursionlimit
from collections import deque

setrecursionlimit(10 ** 9)

N = int(input())
ab = [list(map(int, input().split())) for i in range(N - 1)]

# 1 index
graph = [[] for i in range(N + 1)]

for a, b in ab:
    graph[a].append(b)
    graph[b].append(a)

q = deque([])

mod0 = deque([])
mod1 = deque([])
mod2 = deque([])

for i in range(1, N + 1):
    if i % 3 == 0:
        mod0.append(i)
    elif i % 3 == 1:
        mod1.append(i)
    else:
        mod2.append(i)

dist = [-1] * (N + 1)


def bfs(start):
    q.append(start)
    dist[start] = 0

    while q:
        now = q.popleft()

        for node in graph[now]:
            if dist[node] != -1:
                continue
            else:
                dist[node] = dist[now] + 1
                q.append(node)


node_p = [0] * (N + 1)


def modfit(i):
    if even <= N // 3:
        if dist[i] % 2 == 0:
            node_p[i] = mod0.pop()

        else:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    elif odd <= N // 3:
        if dist[i] % 2 != 0:
            node_p[i] = mod0.pop()

        else:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    else:
        if dist[i] % 2 == 0:
            if mod1:
                node_p[i] = mod1.pop()
            else:
                node_p[i] = mod0.pop()
        else:
            if mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    print(node_p[i], end=" ")


odd = 0
even = 0

bfs(1)

for d in dist:
    if d % 2 == 0:
        even += 1
    else:
        odd += 1

for i in range(1, N + 1):
    modfit(i)

print()


Fixed submission:
from sys import stdin, setrecursionlimit
from collections import deque

setrecursionlimit(10 ** 9)

N = int(stdin.readline())
ab = [list(map(int, stdin.readline().split())) for i in range(N - 1)]

# 1 index
graph = [[] for i in range(N + 1)]

for a, b in ab:
    graph[a].append(b)
    graph[b].append(a)

q = deque([])

mod0 = deque([])
mod1 = deque([])
mod2 = deque([])

for k in range(1, N + 1):
    if k % 3 == 0:
        mod0.append(k)
    elif k % 3 == 1:
        mod1.append(k)
    else:
        mod2.append(k)

dist = [-1] * (N + 1)


def bfs(start):
    q.append(start)
    dist[start] = 0

    while q:
        now = q.popleft()

        for node in graph[now]:
            if dist[node] != -1:
                continue
            else:
                dist[node] = dist[now] + 1
                q.append(node)


node_p = [0] * (N + 1)


def modfit(i):
    if even <= N / 3:
        if dist[i] % 2 == 0:
            node_p[i] = mod0.pop()

        else:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    elif odd <= N / 3:
        if dist[i] % 2 != 0:
            node_p[i] = mod0.pop()

        else:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    else:
        if dist[i] % 2 == 0:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod0:
                node_p[i] = mod0.pop()
            else:
                print(-1)
                exit(0)
        else:
            if mod2:
                node_p[i] = mod2.pop()
            elif mod0:
                node_p[i] = mod0.pop()
            else:
                print(-1)
                exit(0)

    print(node_p[i], end=" ")


odd = 0
even = 0

bfs(N)

for i in range (1,N + 1):
    if dist[i] % 2 == 0:
        even += 1
    else:
        odd += 1

for k in range(1, N + 1):
    modfit(k)

print()

Buggy python submission (verdict: Runtime Error):
from sys import stdin, setrecursionlimit
from collections import deque

setrecursionlimit(10 ** 9)

N = int(stdin.readline())
ab = [list(map(int, stdin.readline().split())) for i in range(N - 1)]

# 1 index
graph = [[] for i in range(N + 1)]

for a, b in ab:
    graph[a].append(b)
    graph[b].append(a)

q = deque([])

mod0 = deque([])
mod1 = deque([])
mod2 = deque([])

for i in range(1, N + 1):
    if i % 3 == 0:
        mod0.append(i)
    elif i % 3 == 1:
        mod1.append(i)
    else:
        mod2.append(i)

dist = [-1] * (N + 1)


def bfs(start):
    q.append(start)
    dist[start] = 0

    while q:
        now = q.popleft()

        for node in graph[now]:
            if dist[node] != -1:
                continue
            else:
                dist[node] = dist[now] + 1
                q.append(node)


node_p = [0] * (N + 1)


def modfit(i):
    if even <= N // 3:
        if dist[i] % 2 == 0:
            node_p[i] = mod0.pop()

        else:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    elif odd <= N // 3:
        if dist[i] % 2 != 0:
            node_p[i] = mod0.pop()

        else:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    else:
        if dist[i] % 2 == 0:
            if mod1:
                node_p[i] = mod1.pop()
            else:
                node_p[i] = mod0.pop()
        else:
            if mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    print(node_p[i], end=" ")


odd = 0
even = 0

bfs(1)

for d in dist:
    if d % 2 == 0:
        even += 1
    else:
        odd += 1

for i in range(1, N + 1):
    modfit(i)

print()


Fixed submission:
from sys import stdin, setrecursionlimit
from collections import deque

setrecursionlimit(10 ** 9)

N = int(stdin.readline())
ab = [list(map(int, stdin.readline().split())) for i in range(N - 1)]

# 1 index
graph = [[] for i in range(N + 1)]

for a, b in ab:
    graph[a].append(b)
    graph[b].append(a)

q = deque([])

mod0 = deque([])
mod1 = deque([])
mod2 = deque([])

for k in range(1, N + 1):
    if k % 3 == 0:
        mod0.append(k)
    elif k % 3 == 1:
        mod1.append(k)
    else:
        mod2.append(k)

dist = [-1] * (N + 1)


def bfs(start):
    q.append(start)
    dist[start] = 0

    while q:
        now = q.popleft()

        for node in graph[now]:
            if dist[node] != -1:
                continue
            else:
                dist[node] = dist[now] + 1
                q.append(node)


node_p = [0] * (N + 1)


def modfit(i):
    if even <= N / 3:
        if dist[i] % 2 == 0:
            node_p[i] = mod0.pop()

        else:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    elif odd <= N / 3:
        if dist[i] % 2 != 0:
            node_p[i] = mod0.pop()

        else:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    else:
        if dist[i] % 2 == 0:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod0:
                node_p[i] = mod0.pop()
            else:
                print(-1)
                exit(0)
        else:
            if mod2:
                node_p[i] = mod2.pop()
            elif mod0:
                node_p[i] = mod0.pop()
            else:
                print(-1)
                exit(0)

    print(node_p[i], end=" ")


odd = 0
even = 0

bfs(N)

for i in range (1,N + 1):
    if dist[i] % 2 == 0:
        even += 1
    else:
        odd += 1

for k in range(1, N + 1):
    modfit(k)

print()

Buggy python submission (verdict: Runtime Error):
from sys import stdin
from collections import deque

N = int(stdin.readline())
ab = [list(map(int, stdin.readline().split())) for i in range(N - 1)]

# 1 index
graph = [[] for i in range(N + 1)]

for a, b in ab:
    graph[a].append(b)
    graph[b].append(a)

q = deque([])

mod0 = deque([])
mod1 = deque([])
mod2 = deque([])

for i in range(1, N + 1):
    if i % 3 == 0:
        mod0.append(i)
    elif i % 3 == 1:
        mod1.append(i)
    else:
        mod2.append(i)

dist = [-1] * (N + 1)


def bfs(start):
    q.append(start)
    dist[start] = 0

    while q:
        now = q.popleft()

        for node in graph[now]:
            if dist[node] != -1:
                continue
            else:
                dist[node] = dist[now] + 1
                q.append(node)


node_p = [0] * (N + 1)


def modfit(i):
    if even <= N // 3:
        if dist[i] % 2 == 0:
            node_p[i] = mod0.pop()

        else:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    elif odd <= N // 3:
        if dist[i] % 2 != 0:
            node_p[i] = mod0.pop()

        else:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    else:
        if dist[i] % 2 == 0:
            if mod1:
                node_p[i] = mod1.pop()
            else:
                node_p[i] = mod0.pop()
        else:
            if mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    print(node_p[i], end=" ")


odd = 0
even = 0

bfs(1)

for d in dist:
    if d % 2 == 0:
        even += 1
    else:
        odd += 1

for i in range(1, N + 1):
    modfit(i)

print()


Fixed submission:
from sys import stdin, setrecursionlimit
from collections import deque

setrecursionlimit(10 ** 9)

N = int(stdin.readline())
ab = [list(map(int, stdin.readline().split())) for i in range(N - 1)]

# 1 index
graph = [[] for i in range(N + 1)]

for a, b in ab:
    graph[a].append(b)
    graph[b].append(a)

q = deque([])

mod0 = deque([])
mod1 = deque([])
mod2 = deque([])

for k in range(1, N + 1):
    if k % 3 == 0:
        mod0.append(k)
    elif k % 3 == 1:
        mod1.append(k)
    else:
        mod2.append(k)

dist = [-1] * (N + 1)


def bfs(start):
    q.append(start)
    dist[start] = 0

    while q:
        now = q.popleft()

        for node in graph[now]:
            if dist[node] != -1:
                continue
            else:
                dist[node] = dist[now] + 1
                q.append(node)


node_p = [0] * (N + 1)


def modfit(i):
    if even <= N / 3:
        if dist[i] % 2 == 0:
            node_p[i] = mod0.pop()

        else:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    elif odd <= N / 3:
        if dist[i] % 2 != 0:
            node_p[i] = mod0.pop()

        else:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    else:
        if dist[i] % 2 == 0:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod0:
                node_p[i] = mod0.pop()
            else:
                print(-1)
                exit(0)
        else:
            if mod2:
                node_p[i] = mod2.pop()
            elif mod0:
                node_p[i] = mod0.pop()
            else:
                print(-1)
                exit(0)

    print(node_p[i], end=" ")


odd = 0
even = 0

bfs(N)

for i in range (1,N + 1):
    if dist[i] % 2 == 0:
        even += 1
    else:
        odd += 1

for k in range(1, N + 1):
    modfit(k)

print()

Buggy python submission (verdict: Runtime Error):
from sys import stdin
from collections import deque

N = int(stdin.readline())
ab = [list(map(int, stdin.readline().split())) for i in range(N - 1)]

# 1 index
graph = [[] for i in range(N + 1)]

for a, b in ab:
    graph[a].append(b)
    graph[b].append(a)

q = deque([])

mod0 = deque([])
mod1 = deque([])
mod2 = deque([])

for i in range(1, N + 1):
    if i % 3 == 0:
        mod0.append(i)
    elif i % 3 == 1:
        mod1.append(i)
    else:
        mod2.append(i)

dist = [-1] * (N + 1)


def bfs(start):
    q.append(start)
    dist[start] = 0

    while q:
        now = q.popleft()

        for node in graph[now]:
            if dist[node] != -1:
                continue
            else:
                dist[node] = dist[now] + 1
                q.append(node)


node_p = [0] * (N + 1)


def modfit(i):
    if even <= N // 3:
        if dist[i] % 2 == 0:
            node_p[i] = mod0.pop()

        else:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    elif odd <= N // 3:
        if dist[i] % 2 != 0:
            node_p[i] = mod0.pop()

        else:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    else:
        if dist[i] % 2 == 0:
            if mod1:
                node_p[i] = mod1.pop()
            else:
                node_p[i] = mod0.pop()
        else:
            if mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()


odd = 0
even = 0

bfs(1)

for d in dist:
    if d % 2 == 0:
        even += 1
    else:
        odd += 1

for i in range(1, N + 1):
    modfit(i)
    print(node_p[i], end=" ")

print()


Fixed submission:
from sys import stdin, setrecursionlimit
from collections import deque

setrecursionlimit(10 ** 9)

N = int(stdin.readline())
ab = [list(map(int, stdin.readline().split())) for i in range(N - 1)]

# 1 index
graph = [[] for i in range(N + 1)]

for a, b in ab:
    graph[a].append(b)
    graph[b].append(a)

q = deque([])

mod0 = deque([])
mod1 = deque([])
mod2 = deque([])

for k in range(1, N + 1):
    if k % 3 == 0:
        mod0.append(k)
    elif k % 3 == 1:
        mod1.append(k)
    else:
        mod2.append(k)

dist = [-1] * (N + 1)


def bfs(start):
    q.append(start)
    dist[start] = 0

    while q:
        now = q.popleft()

        for node in graph[now]:
            if dist[node] != -1:
                continue
            else:
                dist[node] = dist[now] + 1
                q.append(node)


node_p = [0] * (N + 1)


def modfit(i):
    if even <= N / 3:
        if dist[i] % 2 == 0:
            node_p[i] = mod0.pop()

        else:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    elif odd <= N / 3:
        if dist[i] % 2 != 0:
            node_p[i] = mod0.pop()

        else:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod2:
                node_p[i] = mod2.pop()
            else:
                node_p[i] = mod0.pop()

    else:
        if dist[i] % 2 == 0:
            if mod1:
                node_p[i] = mod1.pop()
            elif mod0:
                node_p[i] = mod0.pop()
            else:
                print(-1)
                exit(0)
        else:
            if mod2:
                node_p[i] = mod2.pop()
            elif mod0:
                node_p[i] = mod0.pop()
            else:
                print(-1)
                exit(0)

    print(node_p[i], end=" ")


odd = 0
even = 0

bfs(N)

for i in range (1,N + 1):
    if dist[i] % 2 == 0:
        even += 1
    else:
        odd += 1

for k in range(1, N + 1):
    modfit(k)

print()