Buggy python submission (verdict: Time Limit Exceeded):
import sys
readline = sys.stdin.readline

N = int(readline())
A = [None] * N
for i in range(N):
  # 後ろからpopできるように逆順リストで持つ
  A[i] = list(map(lambda x:x - 1,map(int,readline().split())))[::-1]
  
# 今日試合ができる可能性がある人リスト
candi = set(range(N))

day = 0
while True:
  day += 1
  nex = set()
  done = set()
  for player in candi:
    if player in done:
      continue
    # player が試合できるかチェック
    if not A[player]:
      continue
    rival = A[player][-1]
    if rival in done:
      continue
    if A[rival][-1] == player:
      # 試合できる
      A[player].pop()
      A[rival].pop()
      if A[player]:
        nex.add(player)
      done.add(player)
      if A[rival]:
        nex.add(rival)
      done.add(rival)
    else:
      # 試合できないが、明日も試合できる状態
      nex.add(player)
  if len(done) == 0:
    # 一試合もできなかった
    print(-1)
    exit(0)
  if len(nex) == 0:
    print(day)
    exit(0)
  candi = nex

Fixed submission:
N=int(input())
a=[[0 for j in range(N-1)] for i in range(N)]
for i in range(N):
  line=list(map(int,input().split()))
  for j in range(N-1):
    a[i][j]=line[j]-1
  a[i]=a[i][::-1]
    
q=[]

#seen=[[False for j in range(N)] for i in range(N)]

# 選手nが試合できるならqueに入れる
def check(i):
  if len(a[i])==0:
    return False
  j=a[i][-1]
  if a[j][-1]==i:
    q.append([i,j])
  
for i in range(N):
  check(i)
  
from collections import defaultdict

day=0
while q:
  day+=1
 # q=sorted(q)
  prevQ=q.copy()
  q=[]
  matched=defaultdict(list)
  for p in prevQ:
    i=p[0]
    j=p[1]
    if i>j:
      i,j=j,i
    if matched[i]:
      continue
    a[i].pop()
    a[j].pop()
    check(i)
    check(j)
    matched[i].append(j)
    
for i in range(N):
  if len(a[i])!=0:
    print(-1)
    break
else:
  print(day)

Buggy python submission (verdict: Time Limit Exceeded):
import sys
readline = sys.stdin.readline

N = int(readline())
A = [None] * N
for i in range(N):
  # 後ろからpopできるように逆順リストで持つ
  A[i] = list(map(lambda x:x - 1,map(int,readline().split())))[::-1]
  
# 今日試合ができる可能性がある人リスト
candi = set(range(N))

day = 0
while True:
  day += 1
  nex = set()
  done = set()
  for player in candi:
    if player in done:
      continue
    # player が試合できるかチェック
    if not A[player]:
      continue
    rival = A[player][-1]
    if rival in done:
      continue
    if A[rival][-1] == player:
      # 試合できる
      A[player].pop()
      A[rival].pop()
      if A[player]:
        nex.add(player)
      done.add(player)
      if A[rival]:
        nex.add(rival)
      done.add(rival)
    else:
      # 試合できないが、明日も試合できる状態
      nex.add(player)
  if len(done) == 0:
    # 一試合もできなかった
    print(-1)
    exit(0)
  if len(nex) == 0:
    print(day)
    exit(0)
  candi = nex

Fixed submission:
N=int(input())
a=[[0 for j in range(N-1)] for i in range(N)]
for i in range(N):
  line=list(map(int,input().split()))
  for j in range(N-1):
    a[i][j]=line[j]-1
  a[i]=a[i][::-1]
    
q=[]

#seen=[[False for j in range(N)] for i in range(N)]

# 選手nが試合できるならqueに入れる
def check(i):
  if len(a[i])==0:
    return False
  j=a[i][-1]
  if a[j][-1]==i:
    q.append([i,j])
  
for i in range(N):
  check(i)
  
from collections import defaultdict

day=0
while q:
  day+=1
 # q=sorted(q)
  prevQ=q.copy()
  q=[]
  matched=defaultdict(list)
  for p in prevQ:
    i=p[0]
    j=p[1]
    if i>j:
      i,j=j,i
    if matched[i]:
      continue
    a[i].pop()
    a[j].pop()
    check(i)
    check(j)
    matched[i].append(j)
    
for i in range(N):
  if len(a[i])!=0:
    print(-1)
    break
else:
  print(day)

Buggy python submission (verdict: Time Limit Exceeded):
# 試合を頂点とした有向グラフを書く
# 対戦2チームを元に試合ID(頂点番号)に変換できるようにする
# 閉路があるとNGなので-1
# 閉路がない場合は最長経路が答え

import sys
readline = sys.stdin.readline

N = int(readline())

id_dic = {}
next_id = 0
def to_id(a,b):
  if a > b:
    a,b = b,a
  return id_dic[(a,b)]
def convert_to_id(a,b,next_id):
  if a > b:
    a,b = b,a
  if (a,b) not in id_dic:
    id_dic[(a,b)] = next_id
    return next_id + 1
  return next_id

G = [[] for i in range((N * (N - 1)) // 2)] # 試合グラフ
indegree = [0 for i in range((N * (N - 1)) // 2)] # 入次数
for i in range(N):
  A = list(map(int,readline().split()))
  cur = None
  for a in A:
    # i と a - 1の試合
    next_id = convert_to_id(i,a - 1,next_id)
    game = to_id(i,a - 1)
    if cur != None:
      G[cur].append(game)
      indegree[game] += 1 # 試合に対する入次数が1
    cur = game
  
done = [False for i in range((N * (N - 1)) // 2)] # 試合完了
# 各日付ごとに、入次数が0の試合から行っていく
# 入次数が0になった試合を翌日の試合リスト
stack = []
for i in range(len(indegree)):
  if indegree[i] == 0:
    stack.append(i)
# この頂点からスタートしてBFSで、同じ頂点は通らないようにして移動
# 行けない場所があったら閉路あり
if len(stack) == 0:
  print(-1)
  exit(0)
  
from collections import deque
q = deque(stack)
visited = set()
while q:
  v = q.popleft()
  if v in visited:
    continue
  visited.add(v)
  for child in G[v]:
    q.append(child)

if len(visited) != (N * (N - 1)) // 2:
  print(-1)
  exit(0)

# stackに入った頂点からスタートしてグラフの最長経路を求める
# 閉路なしなので、より長い道があれば更新

stack = []
for i in range(len(indegree)):
  if indegree[i] == 0:
    stack.append([i,1])

dist = [0 for i in range((N * (N - 1)) // 2)]
while stack:
  v, d = stack.pop()
  if dist[v] >= d:
    continue
  dist[v] = d
  for child in G[v]:
    stack.append([child, d + 1])
  
print(max(dist))


Fixed submission:
N=int(input())
a=[[0 for j in range(N-1)] for i in range(N)]
for i in range(N):
  line=list(map(int,input().split()))
  for j in range(N-1):
    a[i][j]=line[j]-1
  a[i]=a[i][::-1]
    
q=[]

#seen=[[False for j in range(N)] for i in range(N)]

# 選手nが試合できるならqueに入れる
def check(i):
  if len(a[i])==0:
    return False
  j=a[i][-1]
  if a[j][-1]==i:
    q.append([i,j])
  
for i in range(N):
  check(i)
  
from collections import defaultdict

day=0
while q:
  day+=1
 # q=sorted(q)
  prevQ=q.copy()
  q=[]
  matched=defaultdict(list)
  for p in prevQ:
    i=p[0]
    j=p[1]
    if i>j:
      i,j=j,i
    if matched[i]:
      continue
    a[i].pop()
    a[j].pop()
    check(i)
    check(j)
    matched[i].append(j)
    
for i in range(N):
  if len(a[i])!=0:
    print(-1)
    break
else:
  print(day)

Buggy python submission (verdict: Time Limit Exceeded):
# 試合を頂点とした有向グラフを書く
# 対戦2チームを元に試合ID(頂点番号)に変換できるようにする
# 閉路があるとNGなので-1
# 閉路がない場合は最長経路が答え

import sys
readline = sys.stdin.readline

N = int(readline())

id_dic = {}
next_id = 0
def to_id(a,b):
  if a > b:
    a,b = b,a
  return id_dic[(a,b)]
def convert_to_id(a,b,next_id):
  if a > b:
    a,b = b,a
  if (a,b) not in id_dic:
    id_dic[(a,b)] = next_id
    return next_id + 1
  return next_id

G = [[] for i in range((N * (N - 1)) // 2)] # 試合グラフ
indegree = [0 for i in range((N * (N - 1)) // 2)] # 入次数
for i in range(N):
  A = list(map(int,readline().split()))
  cur = None
  for a in A:
    # i と a - 1の試合
    next_id = convert_to_id(i,a - 1,next_id)
    game = to_id(i,a - 1)
    if cur != None:
      G[cur].append(game)
      indegree[game] += 1 # 試合に対する入次数が1
    cur = game
  
done = [False for i in range((N * (N - 1)) // 2)] # 試合完了
# 各日付ごとに、入次数が0の試合から行っていく
  
# stackに入った頂点からスタートしてグラフの最長経路を求める
# 閉路なしなので、より長い道があれば更新

# 入次数が0になった試合を翌日の試合リスト
stack = []
for i in range(len(indegree)):
  if indegree[i] == 0:
    stack.append([i,1])

if len(stack) == 0:
  print(-1)
  exit(0)

dist = [-1 for i in range((N * (N - 1)) // 2)]
while stack:
  v, d = stack.pop()
  if dist[v] >= d:
    continue
  dist[v] = d
  for child in G[v]:
    stack.append([child, d + 1])

for d in dist:
  if d == -1:
    print(-1)
    break
else:
  print(max(dist))

Fixed submission:
N=int(input())
a=[[0 for j in range(N-1)] for i in range(N)]
for i in range(N):
  line=list(map(int,input().split()))
  for j in range(N-1):
    a[i][j]=line[j]-1
  a[i]=a[i][::-1]
    
q=[]

#seen=[[False for j in range(N)] for i in range(N)]

# 選手nが試合できるならqueに入れる
def check(i):
  if len(a[i])==0:
    return False
  j=a[i][-1]
  if a[j][-1]==i:
    q.append([i,j])
  
for i in range(N):
  check(i)
  
from collections import defaultdict

day=0
while q:
  day+=1
 # q=sorted(q)
  prevQ=q.copy()
  q=[]
  matched=defaultdict(list)
  for p in prevQ:
    i=p[0]
    j=p[1]
    if i>j:
      i,j=j,i
    if matched[i]:
      continue
    a[i].pop()
    a[j].pop()
    check(i)
    check(j)
    matched[i].append(j)
    
for i in range(N):
  if len(a[i])!=0:
    print(-1)
    break
else:
  print(day)

Buggy python submission (verdict: Time Limit Exceeded):
# 試合を頂点とした有向グラフを書く
# 対戦2チームを元に試合ID(頂点番号)に変換できるようにする
# 閉路があるとNGなので-1
# 閉路がない場合は最長経路が答え

import sys
readline = sys.stdin.readline

N = int(readline())

id_dic = {}
next_id = 0
def to_id(a,b):
  if a > b:
    a,b = b,a
  return id_dic[(a,b)]
def convert_to_id(a,b,next_id):
  if a > b:
    a,b = b,a
  if (a,b) not in id_dic:
    id_dic[(a,b)] = next_id
    return next_id + 1
  return next_id

G = [[] for i in range((N * (N - 1)) // 2)] # 試合グラフ
indegree = [0 for i in range((N * (N - 1)) // 2)] # 入次数
for i in range(N):
  A = list(map(int,readline().split()))
  cur = None
  for a in A:
    # i と a - 1の試合
    next_id = convert_to_id(i,a - 1,next_id)
    game = to_id(i,a - 1)
    if cur != None:
      G[cur].append(game)
      indegree[game] += 1 # 試合に対する入次数が1
    cur = game
  
done = [False for i in range((N * (N - 1)) // 2)] # 試合完了
# 各日付ごとに、入次数が0の試合から行っていく
# 入次数が0になった試合を翌日の試合リスト
stack = []
for i in range(len(indegree)):
  if indegree[i] == 0:
    stack.append(i)
# この頂点からスタートしてBFSで、同じ頂点は通らないようにして移動
# 行けない場所があったら閉路あり
if len(stack) == 0:
  print(-1)
  exit(0)
  
from collections import deque
q = deque(stack)
visited = set()
while q:
  v = q.popleft()
  if v in visited:
    continue
  visited.add(v)
  for child in G[v]:
    q.append(child)

if len(visited) != (N * (N - 1)) // 2:
  print(-1)
  exit(0)

# stackに入った頂点からスタートしてグラフの最長経路を求める
# 閉路なしなので、より長い道があれば更新

stack = []
for i in range(len(indegree)):
  if indegree[i] == 0:
    stack.append([i,1])

dist = [0 for i in range((N * (N - 1)) // 2)]
while stack:
  v, d = stack.pop()
  if dist[v] >= d:
    continue
  dist[v] = d
  for child in G[v]:
    stack.append([child, d + 1])
  
print(max(dist))

Fixed submission:
N=int(input())
a=[[0 for j in range(N-1)] for i in range(N)]
for i in range(N):
  line=list(map(int,input().split()))
  for j in range(N-1):
    a[i][j]=line[j]-1
  a[i]=a[i][::-1]
    
q=[]

#seen=[[False for j in range(N)] for i in range(N)]

# 選手nが試合できるならqueに入れる
def check(i):
  if len(a[i])==0:
    return False
  j=a[i][-1]
  if a[j][-1]==i:
    q.append([i,j])
  
for i in range(N):
  check(i)
  
from collections import defaultdict

day=0
while q:
  day+=1
 # q=sorted(q)
  prevQ=q.copy()
  q=[]
  matched=defaultdict(list)
  for p in prevQ:
    i=p[0]
    j=p[1]
    if i>j:
      i,j=j,i
    if matched[i]:
      continue
    a[i].pop()
    a[j].pop()
    check(i)
    check(j)
    matched[i].append(j)
    
for i in range(N):
  if len(a[i])!=0:
    print(-1)
    break
else:
  print(day)

Buggy python submission (verdict: Time Limit Exceeded):
# 試合を頂点とした有向グラフを書く
# 対戦2チームを元に試合ID(頂点番号)に変換できるようにする
# 閉路があるとNGなので-1
# 閉路がない場合は最長経路が答え

import sys
readline = sys.stdin.readline

N = int(readline())

to_id = [[-1] * N for i in range(N)]
next_id = 0
def convert_to_id(a,b,next_id):
  if to_id[a][b] == -1:
    to_id[a][b] = next_id
    to_id[b][a] = next_id
    return next_id + 1
  return next_id

G = [[] for i in range((N * (N - 1)) // 2)] # 試合グラフ
indegree = [0 for i in range((N * (N - 1)) // 2)] # 入次数
for i in range(N):
  A = list(map(int,readline().split()))
  cur = None
  for a in A:
    # i と a - 1の試合
    next_id = convert_to_id(i,a - 1,next_id)
    game = to_id[i][a - 1]
    if cur != None:
      G[cur].append(game)
      indegree[game] += 1 # 試合に対する入次数が1
    cur = game

done = set()
# 各日付ごとに、入次数が0の試合から行っていく
# 入次数が0になった試合を翌日の試合リスト
stack = []
for i in range(len(indegree)):
  if indegree[i] == 0:
    stack.append(i)

if len(stack) == 0:
  print(-1)
  exit(0)
  
day = 0
while stack:
  day += 1
  nextday = []
  while stack:
    game = stack.pop()
    if game in done: # 既に終わっている試合の場合　閉路と見なす
      print(-1)
      exit(0)
    done.add(game)
    for child in G[game]: # 翌日のゲームを探索
      indegree[child] -= 1
      if indegree[child] == 0: # 入次数が0になれば翌日試合できる
        nextday.append(child)
  stack = nextday

if len(done) != ((N * (N - 1)) // 2):
  print(-1)
  exit(0)
print(day)

Fixed submission:
N=int(input())
a=[[0 for j in range(N-1)] for i in range(N)]
for i in range(N):
  line=list(map(int,input().split()))
  for j in range(N-1):
    a[i][j]=line[j]-1
  a[i]=a[i][::-1]
    
q=[]

#seen=[[False for j in range(N)] for i in range(N)]

# 選手nが試合できるならqueに入れる
def check(i):
  if len(a[i])==0:
    return False
  j=a[i][-1]
  if a[j][-1]==i:
    q.append([i,j])
  
for i in range(N):
  check(i)
  
from collections import defaultdict

day=0
while q:
  day+=1
 # q=sorted(q)
  prevQ=q.copy()
  q=[]
  matched=defaultdict(list)
  for p in prevQ:
    i=p[0]
    j=p[1]
    if i>j:
      i,j=j,i
    if matched[i]:
      continue
    a[i].pop()
    a[j].pop()
    check(i)
    check(j)
    matched[i].append(j)
    
for i in range(N):
  if len(a[i])!=0:
    print(-1)
    break
else:
  print(day)

Buggy python submission (verdict: Time Limit Exceeded):
# 試合を頂点とした有向グラフを書く
# 対戦2チームを元に試合ID(頂点番号)に変換できるようにする
# 閉路があるとNGなので-1
# 閉路がない場合は最長経路が答え

import sys
readline = sys.stdin.readline

N = int(readline())

to_id = {}
next_id = 0
def convert_to_id(a,b,next_id):
  if (a,b) not in to_id:
    to_id[(a,b)] = next_id
    to_id[(b,a)] = next_id
    return next_id + 1
  return next_id

G = [[] for i in range((N * (N - 1)) // 2)] # 試合グラフ
indegree = [0 for i in range((N * (N - 1)) // 2)] # 入次数
for i in range(N):
  A = list(map(int,readline().split()))
  cur = None
  for a in A:
    # i と a - 1の試合
    next_id = convert_to_id(i,a - 1,next_id)
    game = to_id[(i,a - 1)]
    if cur != None:
      G[cur].append(game)
      indegree[game] += 1 # 試合に対する入次数が1
    cur = game

done = set()
# 各日付ごとに、入次数が0の試合から行っていく
# 入次数が0になった試合を翌日の試合リスト
stack = []
for i in range(len(indegree)):
  if indegree[i] == 0:
    stack.append(i)

if len(stack) == 0:
  print(-1)
  exit(0)
  
day = 0
while stack:
  day += 1
  nextday = []
  while stack:
    game = stack.pop()
    if game in done: # 既に終わっている試合の場合　閉路と見なす
      print(-1)
      exit(0)
    done.add(game)
    for child in G[game]: # 翌日のゲームを探索
      indegree[child] -= 1
      if indegree[child] == 0: # 入次数が0になれば翌日試合できる
        nextday.append(child)
  stack = nextday

if len(done) != ((N * (N - 1)) // 2):
  print(-1)
  exit(0)
print(day)

Fixed submission:
N=int(input())
a=[[0 for j in range(N-1)] for i in range(N)]
for i in range(N):
  line=list(map(int,input().split()))
  for j in range(N-1):
    a[i][j]=line[j]-1
  a[i]=a[i][::-1]
    
q=[]

#seen=[[False for j in range(N)] for i in range(N)]

# 選手nが試合できるならqueに入れる
def check(i):
  if len(a[i])==0:
    return False
  j=a[i][-1]
  if a[j][-1]==i:
    q.append([i,j])
  
for i in range(N):
  check(i)
  
from collections import defaultdict

day=0
while q:
  day+=1
 # q=sorted(q)
  prevQ=q.copy()
  q=[]
  matched=defaultdict(list)
  for p in prevQ:
    i=p[0]
    j=p[1]
    if i>j:
      i,j=j,i
    if matched[i]:
      continue
    a[i].pop()
    a[j].pop()
    check(i)
    check(j)
    matched[i].append(j)
    
for i in range(N):
  if len(a[i])!=0:
    print(-1)
    break
else:
  print(day)

Buggy python submission (verdict: Time Limit Exceeded):
# 試合を頂点とした有向グラフを書く
# 対戦2チームを元に試合ID(頂点番号)に変換できるようにする
# 閉路があるとNGなので-1
# 閉路がない場合は最長経路が答え

import sys
readline = sys.stdin.readline

N = int(readline())

id_dic = {}
next_id = 0
def to_id(a,b):
  if a > b:
    a,b = b,a
  return id_dic[(a,b)]
def convert_to_id(a,b,next_id):
  if a > b:
    a,b = b,a
  if (a,b) not in id_dic:
    id_dic[(a,b)] = next_id
    return next_id + 1
  return next_id

G = [[] for i in range((N * (N - 1)) // 2)] # 試合グラフ
indegree = [0 for i in range((N * (N - 1)) // 2)] # 入次数
for i in range(N):
  A = list(map(int,readline().split()))
  cur = None
  for a in A:
    # i と a - 1の試合
    next_id = convert_to_id(i,a - 1,next_id)
    game = to_id(i,a - 1)
    if cur != None:
      G[cur].append(game)
      indegree[game] += 1 # 試合に対する入次数が1
    cur = game

done = set()
# 各日付ごとに、入次数が0の試合から行っていく
# 入次数が0になった試合を翌日の試合リスト
stack = []
for i in range(len(indegree)):
  if indegree[i] == 0:
    stack.append(i)

if len(stack) == 0:
  print(-1)
  exit(0)
  
day = 0
while stack:
  day += 1
  nextday = []
  while stack:
    game = stack.pop()
    if game in done: # 既に終わっている試合の場合　閉路と見なす
      print(-1)
      exit(0)
    done.add(game)
    for child in G[game]: # 翌日のゲームを探索
      indegree[child] -= 1
      if indegree[child] == 0: # 入次数が0になれば翌日試合できる
        nextday.append(child)
  stack = nextday

if len(done) != ((N * (N - 1)) // 2):
  print(-1)
  exit(0)
print(day)

Fixed submission:
N=int(input())
a=[[0 for j in range(N-1)] for i in range(N)]
for i in range(N):
  line=list(map(int,input().split()))
  for j in range(N-1):
    a[i][j]=line[j]-1
  a[i]=a[i][::-1]
    
q=[]

#seen=[[False for j in range(N)] for i in range(N)]

# 選手nが試合できるならqueに入れる
def check(i):
  if len(a[i])==0:
    return False
  j=a[i][-1]
  if a[j][-1]==i:
    q.append([i,j])
  
for i in range(N):
  check(i)
  
from collections import defaultdict

day=0
while q:
  day+=1
 # q=sorted(q)
  prevQ=q.copy()
  q=[]
  matched=defaultdict(list)
  for p in prevQ:
    i=p[0]
    j=p[1]
    if i>j:
      i,j=j,i
    if matched[i]:
      continue
    a[i].pop()
    a[j].pop()
    check(i)
    check(j)
    matched[i].append(j)
    
for i in range(N):
  if len(a[i])!=0:
    print(-1)
    break
else:
  print(day)

Buggy python submission (verdict: Time Limit Exceeded):
# 試合を頂点とした有向グラフを書く
# 対戦2チームを元に試合ID(頂点番号)に変換できるようにする
# 閉路があるとNGなので-1
# 閉路がない場合は最長経路が答え

import sys
readline = sys.stdin.readline

N = int(readline())

id_dic = {}
next_id = 0
def to_id(a,b):
  if a > b:
    a,b = b,a
  return id_dic[(a,b)]
def convert_to_id(a,b,next_id):
  if a > b:
    a,b = b,a
  if (a,b) not in id_dic:
    id_dic[(a,b)] = next_id
    return next_id + 1
  return next_id

G = [[] for i in range((N * (N - 1)) // 2)] # 試合グラフ
indegree = [0 for i in range((N * (N - 1)) // 2)] # 入次数
for i in range(N):
  A = list(map(int,readline().split()))
  cur = None
  for a in A:
    # i と a - 1の試合
    next_id = convert_to_id(i,a - 1,next_id)
    game = to_id(i,a - 1)
    if cur != None:
      G[cur].append(game)
      indegree[game] += 1 # 試合に対する入次数が1
    cur = game
  
done = [False for i in range((N * (N - 1)) // 2)] # 試合完了
# 各日付ごとに、入次数が0の試合から行っていく
# 入次数が0になった試合を翌日の試合リスト
stack = []
for i in range(len(indegree)):
  if indegree[i] == 0:
    stack.append(i)

if len(stack) == 0:
  print(-1)
  exit(0)
  
day = 0
while stack:
  day += 1
  nextday = []
  while stack:
    game = stack.pop()
    if done[game]: # 既に終わっている試合の場合　閉路と見なす
      print(-1)
      exit(0)
    done[game] = True
    for child in G[game]: # 翌日のゲームを探索
      indegree[child] -= 1
      if indegree[child] == 0: # 入次数が0になれば翌日試合できる
        nextday.append(child)
  stack = nextday

if sum(done) != ((N * (N - 1)) // 2):
  print(-1)
  exit(0)
print(day)

Fixed submission:
N=int(input())
a=[[0 for j in range(N-1)] for i in range(N)]
for i in range(N):
  line=list(map(int,input().split()))
  for j in range(N-1):
    a[i][j]=line[j]-1
  a[i]=a[i][::-1]
    
q=[]

#seen=[[False for j in range(N)] for i in range(N)]

# 選手nが試合できるならqueに入れる
def check(i):
  if len(a[i])==0:
    return False
  j=a[i][-1]
  if a[j][-1]==i:
    q.append([i,j])
  
for i in range(N):
  check(i)
  
from collections import defaultdict

day=0
while q:
  day+=1
 # q=sorted(q)
  prevQ=q.copy()
  q=[]
  matched=defaultdict(list)
  for p in prevQ:
    i=p[0]
    j=p[1]
    if i>j:
      i,j=j,i
    if matched[i]:
      continue
    a[i].pop()
    a[j].pop()
    check(i)
    check(j)
    matched[i].append(j)
    
for i in range(N):
  if len(a[i])!=0:
    print(-1)
    break
else:
  print(day)

Buggy python submission (verdict: Time Limit Exceeded):
N=int(input())

a=[[0 for j in range(N-1)] for i in range(N)]
for i in range(N):
  line=list(map(int,input().split()))
  for j in range(N-1):
    a[i][j]=line[j]-1

id=[[0 for j in range(N)] for i in range(N)]
v=0
for i in range(N-1):
  for j in range(i+1,N):
    id[i][j]=v
    v+=1

def toId(i,j):
  if i>j:
    i,j=j,i
  return id[i][j]

to=[[] for i in range(v)]
inner=[0 for i in range(v)]
for i in range(N):
  for j in range(N-1):
    a[i][j]=toId(i,a[i][j])
  for j in range(N-2):
    to[a[i][j]].append(a[i][j+1])
    inner[a[i][j+1]]+=1

stack=[]
isstarted=[False for i in range(v)]
dist=[0 for i in range(v)]
for i in range(v):
  if inner[i]==0:
    stack.append([i,1])

while stack:
  node=stack.pop()
  e=node[0]
  d=node[1]
  if d>dist[e]:
    dist[e]=d
  inner[e]-=1
  if inner[e]<=0 and not isstarted[e]:
    isstarted[e]=True
    children=to[e]
    for child in children:
      stack.append([child,dist[e]+1])
for i in range(len(isstarted)):
  if not isstarted[i]:
    print(-1)
    break
else:
  ans=0
  for i in range(len(dist)):
    if dist[i]>ans:
      ans=dist[i]
  print(ans)

Fixed submission:
N=int(input())
a=[[0 for j in range(N-1)] for i in range(N)]
for i in range(N):
  line=list(map(int,input().split()))
  for j in range(N-1):
    a[i][j]=line[j]-1
  a[i]=a[i][::-1]
    
q=[]

#seen=[[False for j in range(N)] for i in range(N)]

# 選手nが試合できるならqueに入れる
def check(i):
  if len(a[i])==0:
    return False
  j=a[i][-1]
  if a[j][-1]==i:
    q.append([i,j])
  
for i in range(N):
  check(i)
  
from collections import defaultdict

day=0
while q:
  day+=1
 # q=sorted(q)
  prevQ=q.copy()
  q=[]
  matched=defaultdict(list)
  for p in prevQ:
    i=p[0]
    j=p[1]
    if i>j:
      i,j=j,i
    if matched[i]:
      continue
    a[i].pop()
    a[j].pop()
    check(i)
    check(j)
    matched[i].append(j)
    
for i in range(N):
  if len(a[i])!=0:
    print(-1)
    break
else:
  print(day)

Buggy python submission (verdict: Time Limit Exceeded):
N=int(input())
MAXN=1005
MAXV=N*(N-1)//2

a=[[0 for j in range(N-1)] for i in range(N)]
for i in range(N):
  line=list(map(int,input().split()))
  for j in range(N-1):
    a[i][j]=line[j]-1

id=[[0 for j in range(MAXN)] for i in range(MAXN)]
v=0
for i in range(N-1):
  for j in range(i+1,N):
    id[i][j]=v
    v+=1

def toId(i,j):
  if i>j:
    i,j=j,i
  return id[i][j]

to=[[] for i in range(MAXV)]
inner=[0 for i in range(MAXV)]
for i in range(N):
  for j in range(N-1):
    a[i][j]=toId(i,a[i][j])
  for j in range(N-2):
    to[a[i][j]].append(a[i][j+1])
    inner[a[i][j+1]]+=1

ans=0
stack=[]
isstarted=[False for i in range(v)]
dist=[0 for i in range(v)]
for i in range(v):
  if inner[i]==0:
    stack.append([i,1])

while stack:
  node=stack.pop()
  e=node[0]
  d=node[1]
  if d>dist[e]:
    dist[e]=d
  else:
    d=dist[e]
  if dist[e]>ans:
    ans=dist[e]
  inner[e]-=1
  if inner[e]<=0 and not isstarted[e]:
    isstarted[e]=True
    children=to[e]
    for child in children:
      stack.append([child,d+1])
for i in range(len(isstarted)):
  if not isstarted[i]:
    print(-1)
    break
else:
  print(ans)


Fixed submission:
N=int(input())
a=[[0 for j in range(N-1)] for i in range(N)]
for i in range(N):
  line=list(map(int,input().split()))
  for j in range(N-1):
    a[i][j]=line[j]-1
  a[i]=a[i][::-1]
    
q=[]

#seen=[[False for j in range(N)] for i in range(N)]

# 選手nが試合できるならqueに入れる
def check(i):
  if len(a[i])==0:
    return False
  j=a[i][-1]
  if a[j][-1]==i:
    q.append([i,j])
  
for i in range(N):
  check(i)
  
from collections import defaultdict

day=0
while q:
  day+=1
 # q=sorted(q)
  prevQ=q.copy()
  q=[]
  matched=defaultdict(list)
  for p in prevQ:
    i=p[0]
    j=p[1]
    if i>j:
      i,j=j,i
    if matched[i]:
      continue
    a[i].pop()
    a[j].pop()
    check(i)
    check(j)
    matched[i].append(j)
    
for i in range(N):
  if len(a[i])!=0:
    print(-1)
    break
else:
  print(day)

Buggy python submission (verdict: Time Limit Exceeded):
import sys
sys.setrecursionlimit(1000000)
N=int(input())
MAXN=1005
MAXV=N*(N-1)//2

a=[[0 for j in range(N-1)] for i in range(N)]
for i in range(N):
  line=list(map(int,input().split()))
  for j in range(N-1):
    a[i][j]=line[j]-1

id=[[0 for j in range(MAXN)] for i in range(MAXN)]
v=0
for i in range(N-1):
  for j in range(i+1,N):
    id[i][j]=v
    v+=1

def toId(i,j):
  if i>j:
    i,j=j,i
  return id[i][j]

to=[[] for i in range(MAXV)]
for i in range(N):
  for j in range(N-1):
    a[i][j]=toId(i,a[i][j])
  for j in range(N-2):
    to[a[i][j+1]].append(a[i][j])
    
visited=[False for i in range(MAXV)]
calculated=[False for i in range(MAXV)]
dp=[0 for i in range(MAXV)]

def dfs(v):
  if visited[v]:
    if not calculated[v]:
      return -1
    return dp[v]
  visited[v]=True
  for u in to[v]:
    val=dfs(u)
    if val==-1:
      return -1
    if val+1>dp[v]:
      dp[v]=val+1
  calculated[v]=True
  return dp[v]
    
ans=0
for i in range(v):
  res=dfs(i)
  if res==-1:
    print(-1)
    break
  if ans<res:
    ans=res
else:
  print(ans+1)

Fixed submission:
N=int(input())
a=[[0 for j in range(N-1)] for i in range(N)]
for i in range(N):
  line=list(map(int,input().split()))
  for j in range(N-1):
    a[i][j]=line[j]-1
  a[i]=a[i][::-1]
    
q=[]

#seen=[[False for j in range(N)] for i in range(N)]

# 選手nが試合できるならqueに入れる
def check(i):
  if len(a[i])==0:
    return False
  j=a[i][-1]
  if a[j][-1]==i:
    q.append([i,j])
  
for i in range(N):
  check(i)
  
from collections import defaultdict

day=0
while q:
  day+=1
 # q=sorted(q)
  prevQ=q.copy()
  q=[]
  matched=defaultdict(list)
  for p in prevQ:
    i=p[0]
    j=p[1]
    if i>j:
      i,j=j,i
    if matched[i]:
      continue
    a[i].pop()
    a[j].pop()
    check(i)
    check(j)
    matched[i].append(j)
    
for i in range(N):
  if len(a[i])!=0:
    print(-1)
    break
else:
  print(day)

Buggy python submission (verdict: Runtime Error):
N=int(input())
MAXN=1005
MAXV=N*(N-1)//2

a=[[0 for j in range(N-1)] for i in range(N)]
for i in range(N):
  line=list(map(int,input().split()))
  for j in range(N-1):
    a[i][j]=line[j]-1

id=[[0 for j in range(MAXN)] for i in range(MAXN)]
v=0
for i in range(N-1):
  for j in range(i+1,N):
    id[i][j]=v
    v+=1

def toId(i,j):
  if i>j:
    i,j=j,i
  return id[i][j]

to=[[] for i in range(MAXV)]
for i in range(N):
  for j in range(N-1):
    a[i][j]=toId(i,a[i][j])
  for j in range(N-2):
    to[a[i][j+1]].append(a[i][j])
    
visited=[False for i in range(MAXV)]
calculated=[False for i in range(MAXV)]
dp=[0 for i in range(MAXV)]

def dfs(v):
  if visited[v]:
    if not calculated[v]:
      return -1
    return dp[v]
  visited[v]=True
  for u in to[v]:
    val=dfs(u)
    if val==-1:
      return -1
    if val+1>dp[v]:
      dp[v]=val+1
  calculated[v]=True
  return dp[v]
    
ans=0
for i in range(v):
  res=dfs(i)
  if res==-1:
    print(-1)
    break
  if ans<res:
    ans=res
else:
  print(ans+1)


Fixed submission:
N=int(input())
a=[[0 for j in range(N-1)] for i in range(N)]
for i in range(N):
  line=list(map(int,input().split()))
  for j in range(N-1):
    a[i][j]=line[j]-1
  a[i]=a[i][::-1]
    
q=[]

#seen=[[False for j in range(N)] for i in range(N)]

# 選手nが試合できるならqueに入れる
def check(i):
  if len(a[i])==0:
    return False
  j=a[i][-1]
  if a[j][-1]==i:
    q.append([i,j])
  
for i in range(N):
  check(i)
  
from collections import defaultdict

day=0
while q:
  day+=1
 # q=sorted(q)
  prevQ=q.copy()
  q=[]
  matched=defaultdict(list)
  for p in prevQ:
    i=p[0]
    j=p[1]
    if i>j:
      i,j=j,i
    if matched[i]:
      continue
    a[i].pop()
    a[j].pop()
    check(i)
    check(j)
    matched[i].append(j)
    
for i in range(N):
  if len(a[i])!=0:
    print(-1)
    break
else:
  print(day)

Buggy python submission (verdict: Runtime Error):
N=int(input())
MAXN=N+5
MAXV=N*(N-1)//2

a=[[0 for j in range(N-1)] for i in range(N)]
for i in range(N):
  line=list(map(int,input().split()))
  for j in range(N-1):
    a[i][j]=line[j]-1

id=[[0 for j in range(MAXN)] for i in range(MAXN)]
v=0
for i in range(N-1):
  for j in range(i+1,N):
    id[i][j]=v
    v+=1

def toId(i,j):
  if i>j:
    i,j=j,i
  return id[i][j]

to=[[] for i in range(MAXV)]
for i in range(N):
  for j in range(N-1):
    a[i][j]=toId(i,a[i][j])
  for j in range(N-2):
    to[a[i][j+1]].append(a[i][j])
    
visited=[False for i in range(MAXV)]
calculated=[False for i in range(MAXV)]
dp=[0 for i in range(MAXV)]

def dfs(v):
  if visited[v]:
    if not calculated[v]:
      return -1
    return dp[v]
  visited[v]=True
  for u in to[v]:
    val=dfs(u)
    if val==-1:
      return -1
    if val+1>dp[v]:
      dp[v]=val+1
  calculated[v]=True
  return dp[v]
    
ans=0
for i in range(v):
  res=dfs(i)
  if res==-1:
    print(-1)
    break
  if ans<res:
    ans=res
else:
  print(ans+1)

Fixed submission:
N=int(input())
a=[[0 for j in range(N-1)] for i in range(N)]
for i in range(N):
  line=list(map(int,input().split()))
  for j in range(N-1):
    a[i][j]=line[j]-1
  a[i]=a[i][::-1]
    
q=[]

#seen=[[False for j in range(N)] for i in range(N)]

# 選手nが試合できるならqueに入れる
def check(i):
  if len(a[i])==0:
    return False
  j=a[i][-1]
  if a[j][-1]==i:
    q.append([i,j])
  
for i in range(N):
  check(i)
  
from collections import defaultdict

day=0
while q:
  day+=1
 # q=sorted(q)
  prevQ=q.copy()
  q=[]
  matched=defaultdict(list)
  for p in prevQ:
    i=p[0]
    j=p[1]
    if i>j:
      i,j=j,i
    if matched[i]:
      continue
    a[i].pop()
    a[j].pop()
    check(i)
    check(j)
    matched[i].append(j)
    
for i in range(N):
  if len(a[i])!=0:
    print(-1)
    break
else:
  print(day)

Buggy python submission (verdict: Runtime Error):
N=int(input())
MAXN=N+5
MAXV=N*(N-1)//2

a=[[0 for j in range(N-1)] for i in range(N)]
for i in range(N):
  line=list(map(int,input().split()))
  for j in range(N-1):
    a[i][j]=line[j]-1

id=[[0 for j in range(MAXN)] for i in range(MAXN)]
v=0
for i in range(N-1):
  for j in range(i+1,N):
    id[i][j]=v
    v+=1

def toId(i,j):
  if i>j:
    i,j=j,i
  return id[i][j]

to=[[] for i in range(MAXV)]
for i in range(N):
  for j in range(N-1):
    a[i][j]=toId(i,a[i][j])
  for j in range(N-2):
    to[a[i][j+1]].append(a[i][j])
    
visited=[False for i in range(MAXV)]
calculated=[False for i in range(MAXV)]
dp=[0 for i in range(MAXV)]

def dfs(v):
  if visited[v]:
    if not calculated[v]:
      return -1
    return dp[v]
  visited[v]=True
  for u in to[v]:
    val=dfs(u)
    if val==-1:
      return -1
    if val+1>dp[v]:
      dp[v]=val+1
  calculated[v]=True
  return dp[v]
    
ans=0
for i in range(MAXV):
  res=dfs(i)
  if res==-1:
    print(-1)
    break
  if ans<res:
    ans=res
else:
  print(ans+1)

Fixed submission:
N=int(input())
a=[[0 for j in range(N-1)] for i in range(N)]
for i in range(N):
  line=list(map(int,input().split()))
  for j in range(N-1):
    a[i][j]=line[j]-1
  a[i]=a[i][::-1]
    
q=[]

#seen=[[False for j in range(N)] for i in range(N)]

# 選手nが試合できるならqueに入れる
def check(i):
  if len(a[i])==0:
    return False
  j=a[i][-1]
  if a[j][-1]==i:
    q.append([i,j])
  
for i in range(N):
  check(i)
  
from collections import defaultdict

day=0
while q:
  day+=1
 # q=sorted(q)
  prevQ=q.copy()
  q=[]
  matched=defaultdict(list)
  for p in prevQ:
    i=p[0]
    j=p[1]
    if i>j:
      i,j=j,i
    if matched[i]:
      continue
    a[i].pop()
    a[j].pop()
    check(i)
    check(j)
    matched[i].append(j)
    
for i in range(N):
  if len(a[i])!=0:
    print(-1)
    break
else:
  print(day)

Buggy python submission (verdict: Runtime Error):
N=int(input())
a=[[0 for j in range(N-1)] for i in range(N)]
for i in range(N):
  line=list(map(int,input().split()))
  for j in range(N-1):
    a[i][j]=line[j]-1

id=[[0 for j in range(N+5)] for i in range(N+5)]
v=0
for i in range(N-1):
  for j in range(i+1,N):
    id[i][j]=v
    v+=1

def toId(i,j):
  if i>j:
    i,j=j,i
  return id[i][j]

to=[[] for i in range(N*(N+1)//2)]
for i in range(N):
  for j in range(N-1):
    a[i][j]=toId(i,a[i][j])
  for j in range(N-2):
    to[a[i][j+1]].append(a[i][j])
    
visited=[False for i in range(N*(N-1)//2)]
calculated=[False for i in range(N*(N-1)//2)]
dp=[0 for i in range(N*(N-1)//2)]

def dfs(v):
  if visited[v]:
    if not calculated[v]:
      return -1
    return dp[v]
  visited[v]=True
  for u in to[v]:
    val=dfs(u)
    if val==-1:
      return -1
    if val+1>dp[v]:
      dp[v]=val+1
  calculated[v]=True
  return dp[v]
    
ans=0
for i in range(N*(N-1)//2):
  res=dfs(i)
  if res==-1:
    print(-1)
    break
  if ans<res:
    ans=res
else:
  print(ans+1)

Fixed submission:
N=int(input())
a=[[0 for j in range(N-1)] for i in range(N)]
for i in range(N):
  line=list(map(int,input().split()))
  for j in range(N-1):
    a[i][j]=line[j]-1
  a[i]=a[i][::-1]
    
q=[]

#seen=[[False for j in range(N)] for i in range(N)]

# 選手nが試合できるならqueに入れる
def check(i):
  if len(a[i])==0:
    return False
  j=a[i][-1]
  if a[j][-1]==i:
    q.append([i,j])
  
for i in range(N):
  check(i)
  
from collections import defaultdict

day=0
while q:
  day+=1
 # q=sorted(q)
  prevQ=q.copy()
  q=[]
  matched=defaultdict(list)
  for p in prevQ:
    i=p[0]
    j=p[1]
    if i>j:
      i,j=j,i
    if matched[i]:
      continue
    a[i].pop()
    a[j].pop()
    check(i)
    check(j)
    matched[i].append(j)
    
for i in range(N):
  if len(a[i])!=0:
    print(-1)
    break
else:
  print(day)

Buggy python submission (verdict: Runtime Error):
N=int(input())
a=[[0 for j in range(N-1)] for i in range(N)]
for i in range(N):
  line=list(map(int,input().split()))
  for j in range(N-1):
    a[i][j]=line[j]-1
  a[i]=a[i][::-1]
    
from collections import deque
q=deque()

#seen=[[False for j in range(N)] for i in range(N)]

# 選手nが試合できるならqueに入れる
def check(i):
  if len(a[i])==0:
    return False
  j=a[i][-1]
  if a[j][-1]==i:
    q.append([i,j])
  
for i in range(N):
  check(i)
  
from collections import defaultdict

day=0
while q:
  day+=1
  q=sorted(q)
  prevQ=q.copy()
  q=deque()
  matched=defaultdict(list)
  for p in prevQ:
    i=p[0]
    j=p[1]
    if i>j:
      i,j=j,i
    if matched[i]:
      continue
    a[i].pop()
    a[j].pop()
    check(i)
    check(j)
    matched[i].append(j)
    
for i in range(N):
  if len(a[i])!=0:
    print(-1)
    break
else:
  print(day)

Fixed submission:
N=int(input())
a=[[0 for j in range(N-1)] for i in range(N)]
for i in range(N):
  line=list(map(int,input().split()))
  for j in range(N-1):
    a[i][j]=line[j]-1
  a[i]=a[i][::-1]
    
q=[]

#seen=[[False for j in range(N)] for i in range(N)]

# 選手nが試合できるならqueに入れる
def check(i):
  if len(a[i])==0:
    return False
  j=a[i][-1]
  if a[j][-1]==i:
    q.append([i,j])
  
for i in range(N):
  check(i)
  
from collections import defaultdict

day=0
while q:
  day+=1
 # q=sorted(q)
  prevQ=q.copy()
  q=[]
  matched=defaultdict(list)
  for p in prevQ:
    i=p[0]
    j=p[1]
    if i>j:
      i,j=j,i
    if matched[i]:
      continue
    a[i].pop()
    a[j].pop()
    check(i)
    check(j)
    matched[i].append(j)
    
for i in range(N):
  if len(a[i])!=0:
    print(-1)
    break
else:
  print(day)

Buggy python submission (verdict: Time Limit Exceeded):
N=int(input())
a=[[0 for j in range(N-1)] for i in range(N)]
for i in range(N):
  line=list(map(int,input().split()))
  for j in range(N-1):
    a[i][j]=line[j]-1
  a[i]=a[i][::-1]
    
from collections import deque
q=deque()

#seen=[[False for j in range(N)] for i in range(N)]

# 選手nが試合できるならqueに入れる
def check(i):
  if len(a[i])==0:
    return False
  j=a[i][-1]
  if a[j][-1]==i:
    q.append([i,j])
  
for i in range(N):
  check(i)
  
from collections import defaultdict

day=0
while q:
  day+=1
  q=sorted(q)
  prevQ=q.copy()
  q=deque()
  matched=defaultdict(list)
  for p in prevQ:
    i=p[0]
    j=p[1]
    if i>j:
      i,j=j,i
    if matched[i]:
      continue
    a[i].pop()
    a[j].pop()
    check(i)
    check(j)
    matched[i].append(j)
    
for i in range(N):
  if len(a[i])!=0:
    print(-1)
    break
else:
  print(day)

Fixed submission:
N=int(input())
a=[[0 for j in range(N-1)] for i in range(N)]
for i in range(N):
  line=list(map(int,input().split()))
  for j in range(N-1):
    a[i][j]=line[j]-1
  a[i]=a[i][::-1]
    
q=[]

#seen=[[False for j in range(N)] for i in range(N)]

# 選手nが試合できるならqueに入れる
def check(i):
  if len(a[i])==0:
    return False
  j=a[i][-1]
  if a[j][-1]==i:
    q.append([i,j])
  
for i in range(N):
  check(i)
  
from collections import defaultdict

day=0
while q:
  day+=1
 # q=sorted(q)
  prevQ=q.copy()
  q=[]
  matched=defaultdict(list)
  for p in prevQ:
    i=p[0]
    j=p[1]
    if i>j:
      i,j=j,i
    if matched[i]:
      continue
    a[i].pop()
    a[j].pop()
    check(i)
    check(j)
    matched[i].append(j)
    
for i in range(N):
  if len(a[i])!=0:
    print(-1)
    break
else:
  print(day)

Buggy python submission (verdict: Time Limit Exceeded):
n=int(input())
plan=[None]*n
for i in range(n):
  p=list(map(int,input().split()))
  for j in range(len(p)):
    p[j]=p[j]-1
  plan[i]=p
 
d=0
error=False
while True:
  d=d+1
  done=[True]*n
  thisday=False
  for i in range(n):
    if done[i]==False:
      continue
    if len(plan[i])==0:
      continue
    target=plan[i][0]
    if done[target]==False:
      continue
    if len(plan[target])==0:
      continue
    if plan[target][0]==i:
      # match
      plan[i]=plan[i][1:]
      plan[target]=plan[target][1:]
      done[i]=False
      done[target]=False
      thisday=True
  if thisday==False:
    # no game today
    # check if every plan is finished
    for i in range(len(plan)):
      if len(plan[i])!=0:
        error=True
    break
  
if error:
  print(-1)
else:
  print(d-1)

Fixed submission:
N=int(input())
a=[[0 for j in range(N-1)] for i in range(N)]
for i in range(N):
  line=list(map(int,input().split()))
  for j in range(N-1):
    a[i][j]=line[j]-1
  a[i]=a[i][::-1]
    
q=[]

#seen=[[False for j in range(N)] for i in range(N)]

# 選手nが試合できるならqueに入れる
def check(i):
  if len(a[i])==0:
    return False
  j=a[i][-1]
  if a[j][-1]==i:
    q.append([i,j])
  
for i in range(N):
  check(i)
  
from collections import defaultdict

day=0
while q:
  day+=1
 # q=sorted(q)
  prevQ=q.copy()
  q=[]
  matched=defaultdict(list)
  for p in prevQ:
    i=p[0]
    j=p[1]
    if i>j:
      i,j=j,i
    if matched[i]:
      continue
    a[i].pop()
    a[j].pop()
    check(i)
    check(j)
    matched[i].append(j)
    
for i in range(N):
  if len(a[i])!=0:
    print(-1)
    break
else:
  print(day)

Buggy python submission (verdict: Time Limit Exceeded):
n=int(input())
plan=[None]*n
for i in range(n):
  p=list(map(int,input().split()))
  for j in range(len(p)):
    p[j]=p[j]-1
  plan[i]=p

# print(plan)
d=0
error=False
while True:
  d=d+1
#  print(str(d)+" day")
  done=[True]*n
  thisday=False
  for i in range(n):
    if done[i]==False:
      continue
    if len(plan[i])==0:
      continue
    target=plan[i][0]
    if done[target]==False:
      continue
    if len(plan[target])==0:
      continue
#    print("plan[i]")
#    print(plan[i])
#    print("target:"+str(target))
#    print("plan[target]")
#    print(plan[target])
    if plan[target][0]==i:
      # 試合を行う
#      print(str(i)+":"+str(plan[i][0])+" and "+str(target)+":"+str(plan[target][0])+ "fight!")
      plan[i].pop(0)
      plan[target].pop(0)
      done[i]=False
      done[target]=False
#      print("plan[i],plan[target] after that")
#      print(plan[i])
#      print(plan[target])
      thisday=True
  if thisday==False:
    # 試合が一つも組めなかった
    # ぜんぶからになっているなら正常終了　そうでなければ-1
    for i in range(len(plan)):
      if len(plan[i])!=0:
        error=True
    break
  
if error:
  print(-1)
else:
  print(d-1)

Fixed submission:
N=int(input())
a=[[0 for j in range(N-1)] for i in range(N)]
for i in range(N):
  line=list(map(int,input().split()))
  for j in range(N-1):
    a[i][j]=line[j]-1
  a[i]=a[i][::-1]
    
q=[]

#seen=[[False for j in range(N)] for i in range(N)]

# 選手nが試合できるならqueに入れる
def check(i):
  if len(a[i])==0:
    return False
  j=a[i][-1]
  if a[j][-1]==i:
    q.append([i,j])
  
for i in range(N):
  check(i)
  
from collections import defaultdict

day=0
while q:
  day+=1
 # q=sorted(q)
  prevQ=q.copy()
  q=[]
  matched=defaultdict(list)
  for p in prevQ:
    i=p[0]
    j=p[1]
    if i>j:
      i,j=j,i
    if matched[i]:
      continue
    a[i].pop()
    a[j].pop()
    check(i)
    check(j)
    matched[i].append(j)
    
for i in range(N):
  if len(a[i])!=0:
    print(-1)
    break
else:
  print(day)

Buggy python submission (verdict: Time Limit Exceeded):
n=int(input())
plan=[None]*n
for i in range(n):
  p=list(map(int,input().split()))
  for j in range(len(p)):
    p[j]=p[j]-1
  plan[i]=p

d=0
error=False
while True:
  d=d+1
  done=[True]*n
  thisday=False
  for i in range(n):
    if done[i]==False:
      continue
    if len(plan[i])==0:
      continue
    target=plan[i][0]
    if done[target]==False:
      continue
    if len(plan[target])==0:
      continue
    if plan[target][0]==i:
      # match
      plan[i].pop(0)
      plan[target].pop(0)
      done[i]=False
      done[target]=False
      thisday=True
  if thisday==False:
    # no game today
    # check if every plan is finished
    for i in range(len(plan)):
      if len(plan[i])!=0:
        error=True
    break
  
if error:
  print(-1)
else:
  print(d-1)

Fixed submission:
N=int(input())
a=[[0 for j in range(N-1)] for i in range(N)]
for i in range(N):
  line=list(map(int,input().split()))
  for j in range(N-1):
    a[i][j]=line[j]-1
  a[i]=a[i][::-1]
    
q=[]

#seen=[[False for j in range(N)] for i in range(N)]

# 選手nが試合できるならqueに入れる
def check(i):
  if len(a[i])==0:
    return False
  j=a[i][-1]
  if a[j][-1]==i:
    q.append([i,j])
  
for i in range(N):
  check(i)
  
from collections import defaultdict

day=0
while q:
  day+=1
 # q=sorted(q)
  prevQ=q.copy()
  q=[]
  matched=defaultdict(list)
  for p in prevQ:
    i=p[0]
    j=p[1]
    if i>j:
      i,j=j,i
    if matched[i]:
      continue
    a[i].pop()
    a[j].pop()
    check(i)
    check(j)
    matched[i].append(j)
    
for i in range(N):
  if len(a[i])!=0:
    print(-1)
    break
else:
  print(day)