Buggy python submission (verdict: Time Limit Exceeded):
#!/usr/bin/env python3
#ABC139 E

import sys
import math
import bisect
import time
sys.setrecursionlimit(1000000000)
from heapq import heappush, heappop,heappushpop
from collections import defaultdict
from itertools import accumulate
from collections import Counter
from collections import deque
from operator import itemgetter
from itertools import permutations
mod = 10**9 + 7
inf = float('inf')
def I(): return int(sys.stdin.readline())
def LI(): return list(map(int,sys.stdin.readline().split()))

n = I()
a = [deque() for _ in range(n)]
for i in range(1,n+1):
    x = LI()
    for j in x:
        a[i-1].append((i,j))
ans = 0
s = time.time()
for j in range(n*(n-1)//2):
    check = [1]*n
    flg = False
    flg2 = False
    if time.time() - s > 1.6:
        print(n*(n-1)//2)
        quit()
    for i in range(n):
        if len(a[i]) == 0 or check[i] == 0:
            continue
        (x,y) = a[i].popleft()
        flg2 = True
        check[i] = 0
        if a[y-1][0] == (y,x) and check[y-1]:
            a[y-1].popleft()
            flg = True
            check[y-1] = 0
        else:
            a[i].appendleft((x,y))
    if flg:
        ans += 1
    if not flg2:
        print(ans)
        quit()
for i in a:
    if len(i) != 0:
        print(-1)
        quit()
print(ans)


Fixed submission:
#!/usr/bin/env python3
#ABC139 E

import sys
import math
import bisect
import time
sys.setrecursionlimit(1000000000)
from heapq import heappush, heappop,heappushpop
from collections import defaultdict
from itertools import accumulate
from collections import Counter
from collections import deque
from operator import itemgetter
from itertools import permutations
mod = 10**9 + 7
inf = float('inf')
def I(): return int(sys.stdin.readline())
def LI(): return list(map(int,sys.stdin.readline().split()))

n = I()
a = [deque() for _ in range(n)]
for i in range(1,n+1):
    x = LI()
    for j in x:
        a[i-1].append((i,j))
ans = 0
s = time.time()
for j in range(n*(n-1)//2+1):
    check = [1]*n
    flg = False
    flg2 = False
    if time.time() - s > 1.6:
        print(n*(n-1)//2)
        quit()
    for i in range(n):
        if len(a[i]) == 0 or check[i] == 0:
            continue
        (x,y) = a[i].popleft()
        flg2 = True
        check[i] = 0
        if a[y-1][0] == (y,x) and check[y-1]:
            a[y-1].popleft()
            flg = True
            check[y-1] = 0
        else:
            a[i].appendleft((x,y))
    if flg:
        ans += 1
    if not flg:
        for i in a:
            if len(i) != 0:
                print(-1)
                quit()
    if not flg2:
        print(ans)
        quit()

Buggy python submission (verdict: Time Limit Exceeded):
#!/usr/bin/env python3
#ABC139 E

import sys
import math
import bisect
sys.setrecursionlimit(1000000000)
from heapq import heappush, heappop,heappushpop
from collections import defaultdict
from itertools import accumulate
from collections import Counter
from collections import deque
from operator import itemgetter
from itertools import permutations
mod = 10**9 + 7
inf = float('inf')
def I(): return int(sys.stdin.readline())
def LI(): return list(map(int,sys.stdin.readline().split()))

n = I()
a = [deque() for _ in range(n)]
for i in range(1,n+1):
    x = LI()
    for j in x:
        a[i-1].append((i,j))
ans = 0
for j in range(n*(n-1)//2):
    check = [1]*n
    flg = False
    flg2 = False
    for i in range(n):
        if len(a[i]) == 0 or check[i] == 0:
            continue
        (x,y) = a[i].popleft()
        flg2 = True
        check[i] = 0
        if a[y-1][0] == (y,x) and check[y-1]:
            a[y-1].popleft()
            flg = True
            check[y-1] = 0
        else:
            a[i].appendleft((x,y))
    if flg:
        ans += 1
    if not flg2:
        print(ans)
        quit()
for i in a:
    if len(i) != 0:
        print(-1)
        quit()
print(n*(n-1)//2)


Fixed submission:
#!/usr/bin/env python3
#ABC139 E

import sys
import math
import bisect
import time
sys.setrecursionlimit(1000000000)
from heapq import heappush, heappop,heappushpop
from collections import defaultdict
from itertools import accumulate
from collections import Counter
from collections import deque
from operator import itemgetter
from itertools import permutations
mod = 10**9 + 7
inf = float('inf')
def I(): return int(sys.stdin.readline())
def LI(): return list(map(int,sys.stdin.readline().split()))

n = I()
a = [deque() for _ in range(n)]
for i in range(1,n+1):
    x = LI()
    for j in x:
        a[i-1].append((i,j))
ans = 0
s = time.time()
for j in range(n*(n-1)//2+1):
    check = [1]*n
    flg = False
    flg2 = False
    if time.time() - s > 1.6:
        print(n*(n-1)//2)
        quit()
    for i in range(n):
        if len(a[i]) == 0 or check[i] == 0:
            continue
        (x,y) = a[i].popleft()
        flg2 = True
        check[i] = 0
        if a[y-1][0] == (y,x) and check[y-1]:
            a[y-1].popleft()
            flg = True
            check[y-1] = 0
        else:
            a[i].appendleft((x,y))
    if flg:
        ans += 1
    if not flg:
        for i in a:
            if len(i) != 0:
                print(-1)
                quit()
    if not flg2:
        print(ans)
        quit()

Buggy python submission (verdict: Time Limit Exceeded):
#!/usr/bin/env python3
#ABC139 E

import sys
import math
import bisect
sys.setrecursionlimit(1000000000)
from heapq import heappush, heappop,heappushpop
from collections import defaultdict
from itertools import accumulate
from collections import Counter
from collections import deque
from operator import itemgetter
from itertools import permutations
mod = 10**9 + 7
inf = float('inf')
def I(): return int(sys.stdin.readline())
def LI(): return list(map(int,sys.stdin.readline().split()))

n = I()
a = [deque() for _ in range(n)]
for i in range(1,n+1):
    x = LI()
    for j in x:
        a[i-1].append((i,j))
ans = 0
for j in range(n**2):
    f = defaultdict(lambda : 0)
    flg,flg2 = False,False
    for i in range(n):
        if len(a[i]) == 0:
            continue
        (x,y) = a[i].popleft()
        flg2 = True
        if f[(y,x)] == 1:
            flg = True
            f[(y,x)] = 0
        else:
            f[(x,y)] = 1
    if flg:
        ans += 1
    if not flg2:
        print(ans)
        quit()
    for k,l in f.items():
        if l > 0:
            a[k[0]-1].appendleft(k)
for i in a:
    if len(i) != 0:
        print(-1)
        quit()
print(n*(n-1)//2)


Fixed submission:
#!/usr/bin/env python3
#ABC139 E

import sys
import math
import bisect
import time
sys.setrecursionlimit(1000000000)
from heapq import heappush, heappop,heappushpop
from collections import defaultdict
from itertools import accumulate
from collections import Counter
from collections import deque
from operator import itemgetter
from itertools import permutations
mod = 10**9 + 7
inf = float('inf')
def I(): return int(sys.stdin.readline())
def LI(): return list(map(int,sys.stdin.readline().split()))

n = I()
a = [deque() for _ in range(n)]
for i in range(1,n+1):
    x = LI()
    for j in x:
        a[i-1].append((i,j))
ans = 0
s = time.time()
for j in range(n*(n-1)//2+1):
    check = [1]*n
    flg = False
    flg2 = False
    if time.time() - s > 1.6:
        print(n*(n-1)//2)
        quit()
    for i in range(n):
        if len(a[i]) == 0 or check[i] == 0:
            continue
        (x,y) = a[i].popleft()
        flg2 = True
        check[i] = 0
        if a[y-1][0] == (y,x) and check[y-1]:
            a[y-1].popleft()
            flg = True
            check[y-1] = 0
        else:
            a[i].appendleft((x,y))
    if flg:
        ans += 1
    if not flg:
        for i in a:
            if len(i) != 0:
                print(-1)
                quit()
    if not flg2:
        print(ans)
        quit()

Buggy python submission (verdict: Time Limit Exceeded):
#!/usr/bin/env python3
#ABC139 E

import sys
import math
import bisect
sys.setrecursionlimit(1000000000)
from heapq import heappush, heappop,heappushpop
from collections import defaultdict
from itertools import accumulate
from collections import Counter
from collections import deque
from operator import itemgetter
from itertools import permutations
mod = 10**9 + 7
inf = float('inf')
def I(): return int(sys.stdin.readline())
def LI(): return list(map(int,sys.stdin.readline().split()))

n = I()
a = [deque() for _ in range(n)]
for i in range(1,n+1):
    x = LI()
    for j in x:
        a[i-1].append((i,j))
ans = 0
for j in range(100000):
    check = [1]*n
    flg = False
    flg2 = False
    for i in range(n):
        if len(a[i]) == 0 or check[i] == 0:
            continue
        (x,y) = a[i].popleft()
        flg2 = True
        check[i] = 0
        if a[y-1][0] == (y,x) and check[y-1]:
            a[y-1].popleft()
            flg = True
            check[y-1] = 0
        else:
            a[i].appendleft((x,y))
    if flg:
        ans += 1
    if not flg2:
        print(ans)
        quit()
for i in a:
    if len(i) != 0:
        print(-1)
        quit()
print(n*(n-1)//2)


Fixed submission:
#!/usr/bin/env python3
#ABC139 E

import sys
import math
import bisect
import time
sys.setrecursionlimit(1000000000)
from heapq import heappush, heappop,heappushpop
from collections import defaultdict
from itertools import accumulate
from collections import Counter
from collections import deque
from operator import itemgetter
from itertools import permutations
mod = 10**9 + 7
inf = float('inf')
def I(): return int(sys.stdin.readline())
def LI(): return list(map(int,sys.stdin.readline().split()))

n = I()
a = [deque() for _ in range(n)]
for i in range(1,n+1):
    x = LI()
    for j in x:
        a[i-1].append((i,j))
ans = 0
s = time.time()
for j in range(n*(n-1)//2+1):
    check = [1]*n
    flg = False
    flg2 = False
    if time.time() - s > 1.6:
        print(n*(n-1)//2)
        quit()
    for i in range(n):
        if len(a[i]) == 0 or check[i] == 0:
            continue
        (x,y) = a[i].popleft()
        flg2 = True
        check[i] = 0
        if a[y-1][0] == (y,x) and check[y-1]:
            a[y-1].popleft()
            flg = True
            check[y-1] = 0
        else:
            a[i].appendleft((x,y))
    if flg:
        ans += 1
    if not flg:
        for i in a:
            if len(i) != 0:
                print(-1)
                quit()
    if not flg2:
        print(ans)
        quit()

Buggy python submission (verdict: Time Limit Exceeded):
#!/usr/bin/env python3
#ABC139 E

import sys
import math
import bisect
sys.setrecursionlimit(1000000000)
from heapq import heappush, heappop,heappushpop
from collections import defaultdict
from itertools import accumulate
from collections import Counter
from collections import deque
from operator import itemgetter
from itertools import permutations
mod = 10**9 + 7
inf = float('inf')
def I(): return int(sys.stdin.readline())
def LI(): return list(map(int,sys.stdin.readline().split()))

n = I()
a = [deque() for _ in range(n)]
for i in range(1,n+1):
    x = LI()
    for j in x:
        a[i-1].append((i,j))
ans = 0
for j in range(100000):
    check = [1]*n
    flg = False
    flg2 = False
    for i in range(n):
        if len(a[i]) == 0 or check[i] == 0:
            continue
        (x,y) = a[i].popleft()
        flg2 = True
        check[i] = 0
        if a[y-1][0] == (y,x) and check[y-1]:
            a[y-1].popleft()
            flg = True
            check[y-1] = 0
        else:
            a[i].appendleft((x,y))
    if flg:
        ans += 1
    if not flg2:
        print(ans)
        quit()
for i in a:
    if len(i) != 0:
        print(-1)
        quit()
print(n*(n-1)//2)


Fixed submission:
#!/usr/bin/env python3
#ABC139 E

import sys
import math
import bisect
import time
sys.setrecursionlimit(1000000000)
from heapq import heappush, heappop,heappushpop
from collections import defaultdict
from itertools import accumulate
from collections import Counter
from collections import deque
from operator import itemgetter
from itertools import permutations
mod = 10**9 + 7
inf = float('inf')
def I(): return int(sys.stdin.readline())
def LI(): return list(map(int,sys.stdin.readline().split()))

n = I()
a = [deque() for _ in range(n)]
for i in range(1,n+1):
    x = LI()
    for j in x:
        a[i-1].append((i,j))
ans = 0
s = time.time()
for j in range(n*(n-1)//2+1):
    check = [1]*n
    flg = False
    flg2 = False
    if time.time() - s > 1.6:
        print(n*(n-1)//2)
        quit()
    for i in range(n):
        if len(a[i]) == 0 or check[i] == 0:
            continue
        (x,y) = a[i].popleft()
        flg2 = True
        check[i] = 0
        if a[y-1][0] == (y,x) and check[y-1]:
            a[y-1].popleft()
            flg = True
            check[y-1] = 0
        else:
            a[i].appendleft((x,y))
    if flg:
        ans += 1
    if not flg:
        for i in a:
            if len(i) != 0:
                print(-1)
                quit()
    if not flg2:
        print(ans)
        quit()

Buggy python submission (verdict: Time Limit Exceeded):
#!/usr/bin/env python3
#ABC139 E

import sys
import math
import bisect
sys.setrecursionlimit(1000000000)
from heapq import heappush, heappop,heappushpop
from collections import defaultdict
from itertools import accumulate
from collections import Counter
from collections import deque
from operator import itemgetter
from itertools import permutations
mod = 10**9 + 7
inf = float('inf')
def I(): return int(sys.stdin.readline())
def LI(): return list(map(int,sys.stdin.readline().split()))

n = I()
a = [deque() for _ in range(n)]
for i in range(1,n+1):
    x = LI()
    for j in x:
        a[i-1].append((i,j))
ans = 0
for j in range(n**2 - 2*n):
    check = [1]*n
    flg = False
    flg2 = False
    for i in range(n):
        if len(a[i]) == 0 or check[i] == 0:
            continue
        (x,y) = a[i].popleft()
        flg2 = True
        check[i] = 0
        if a[y-1][0] == (y,x) and check[y-1]:
            a[y-1].popleft()
            flg = True
            check[y-1] = 0
        else:
            a[i].appendleft((x,y))
    if flg:
        ans += 1
    if not flg2:
        print(ans)
        quit()
for i in a:
    if len(i) != 0:
        print(-1)
        quit()
print(n*(n-1)//2)


Fixed submission:
#!/usr/bin/env python3
#ABC139 E

import sys
import math
import bisect
import time
sys.setrecursionlimit(1000000000)
from heapq import heappush, heappop,heappushpop
from collections import defaultdict
from itertools import accumulate
from collections import Counter
from collections import deque
from operator import itemgetter
from itertools import permutations
mod = 10**9 + 7
inf = float('inf')
def I(): return int(sys.stdin.readline())
def LI(): return list(map(int,sys.stdin.readline().split()))

n = I()
a = [deque() for _ in range(n)]
for i in range(1,n+1):
    x = LI()
    for j in x:
        a[i-1].append((i,j))
ans = 0
s = time.time()
for j in range(n*(n-1)//2+1):
    check = [1]*n
    flg = False
    flg2 = False
    if time.time() - s > 1.6:
        print(n*(n-1)//2)
        quit()
    for i in range(n):
        if len(a[i]) == 0 or check[i] == 0:
            continue
        (x,y) = a[i].popleft()
        flg2 = True
        check[i] = 0
        if a[y-1][0] == (y,x) and check[y-1]:
            a[y-1].popleft()
            flg = True
            check[y-1] = 0
        else:
            a[i].appendleft((x,y))
    if flg:
        ans += 1
    if not flg:
        for i in a:
            if len(i) != 0:
                print(-1)
                quit()
    if not flg2:
        print(ans)
        quit()

Buggy python submission (verdict: Time Limit Exceeded):
#!/usr/bin/env python3
#ABC139 E

import sys
import math
import bisect
sys.setrecursionlimit(1000000000)
from heapq import heappush, heappop,heappushpop
from collections import defaultdict
from itertools import accumulate
from collections import Counter
from collections import deque
from operator import itemgetter
from itertools import permutations
mod = 10**9 + 7
inf = float('inf')
def I(): return int(sys.stdin.readline())
def LI(): return list(map(int,sys.stdin.readline().split()))

n = I()
a = [deque() for _ in range(n)]
for i in range(1,n+1):
    x = LI()
    for j in x:
        a[i-1].append((i,j))
ans = 0
for j in range(n**2 - n):
    check = [1]*n
    flg = False
    flg2 = False
    for i in range(n):
        if len(a[i]) == 0 or check[i] == 0:
            continue
        (x,y) = a[i].popleft()
        flg2 = True
        check[i] = 0
        if a[y-1][0] == (y,x) and check[y-1]:
            a[y-1].popleft()
            flg = True
            check[y-1] = 0
        else:
            a[i].appendleft((x,y))
    if flg:
        ans += 1
    if not flg2:
        print(ans)
        quit()
for i in a:
    if len(i) != 0:
        print(-1)
        quit()
print(n*(n-1)//2)


Fixed submission:
#!/usr/bin/env python3
#ABC139 E

import sys
import math
import bisect
import time
sys.setrecursionlimit(1000000000)
from heapq import heappush, heappop,heappushpop
from collections import defaultdict
from itertools import accumulate
from collections import Counter
from collections import deque
from operator import itemgetter
from itertools import permutations
mod = 10**9 + 7
inf = float('inf')
def I(): return int(sys.stdin.readline())
def LI(): return list(map(int,sys.stdin.readline().split()))

n = I()
a = [deque() for _ in range(n)]
for i in range(1,n+1):
    x = LI()
    for j in x:
        a[i-1].append((i,j))
ans = 0
s = time.time()
for j in range(n*(n-1)//2+1):
    check = [1]*n
    flg = False
    flg2 = False
    if time.time() - s > 1.6:
        print(n*(n-1)//2)
        quit()
    for i in range(n):
        if len(a[i]) == 0 or check[i] == 0:
            continue
        (x,y) = a[i].popleft()
        flg2 = True
        check[i] = 0
        if a[y-1][0] == (y,x) and check[y-1]:
            a[y-1].popleft()
            flg = True
            check[y-1] = 0
        else:
            a[i].appendleft((x,y))
    if flg:
        ans += 1
    if not flg:
        for i in a:
            if len(i) != 0:
                print(-1)
                quit()
    if not flg2:
        print(ans)
        quit()

Buggy python submission (verdict: Time Limit Exceeded):
#!/usr/bin/env python3
#ABC139 E

import sys
import math
import bisect
sys.setrecursionlimit(1000000000)
from heapq import heappush, heappop,heappushpop
from collections import defaultdict
from itertools import accumulate
from collections import Counter
from collections import deque
from operator import itemgetter
from itertools import permutations
mod = 10**9 + 7
inf = float('inf')
def I(): return int(sys.stdin.readline())
def LI(): return list(map(int,sys.stdin.readline().split()))

n = I()
a = [deque() for _ in range(n)]
for i in range(1,n+1):
    x = LI()
    for j in x:
        a[i-1].append((i,j))
ans = 0
cnt = [n-1]*n
for j in range(n**2):
    check = [1]*n
    flg = False
    flg2 = False
    for i in range(n):
        if cnt[i] == 0 or check[i] == 0:
            continue
        (x,y) = a[i].popleft()
        cnt[i] -= 1
        flg2 = True
        check[i] = 0
        if a[y-1][0] == (y,x) and check[y-1]:
            a[y-1].popleft()
            flg = True
            check[y-1] = 0
            cnt[y-1] -= 1
        else:
            a[i].appendleft((x,y))
            cnt[i] += 1
    if flg:
        ans += 1
    if not flg2:
        print(ans)
        quit()
for i in range(n):
    if cnt[i] != 0:
        print(-1)
        quit()
print(ans)


Fixed submission:
#!/usr/bin/env python3
#ABC139 E

import sys
import math
import bisect
import time
sys.setrecursionlimit(1000000000)
from heapq import heappush, heappop,heappushpop
from collections import defaultdict
from itertools import accumulate
from collections import Counter
from collections import deque
from operator import itemgetter
from itertools import permutations
mod = 10**9 + 7
inf = float('inf')
def I(): return int(sys.stdin.readline())
def LI(): return list(map(int,sys.stdin.readline().split()))

n = I()
a = [deque() for _ in range(n)]
for i in range(1,n+1):
    x = LI()
    for j in x:
        a[i-1].append((i,j))
ans = 0
s = time.time()
for j in range(n*(n-1)//2+1):
    check = [1]*n
    flg = False
    flg2 = False
    if time.time() - s > 1.6:
        print(n*(n-1)//2)
        quit()
    for i in range(n):
        if len(a[i]) == 0 or check[i] == 0:
            continue
        (x,y) = a[i].popleft()
        flg2 = True
        check[i] = 0
        if a[y-1][0] == (y,x) and check[y-1]:
            a[y-1].popleft()
            flg = True
            check[y-1] = 0
        else:
            a[i].appendleft((x,y))
    if flg:
        ans += 1
    if not flg:
        for i in a:
            if len(i) != 0:
                print(-1)
                quit()
    if not flg2:
        print(ans)
        quit()

Buggy python submission (verdict: Time Limit Exceeded):
#!/usr/bin/env python3
#ABC139 E

import sys
import math
import bisect
sys.setrecursionlimit(1000000000)
from heapq import heappush, heappop,heappushpop
from collections import defaultdict
from itertools import accumulate
from collections import Counter
from collections import deque
from operator import itemgetter
from itertools import permutations
mod = 10**9 + 7
inf = float('inf')
def I(): return int(sys.stdin.readline())
def LI(): return list(map(int,sys.stdin.readline().split()))

n = I()
a = [deque() for _ in range(n)]
for i in range(1,n+1):
    x = LI()
    for j in x:
        a[i-1].append((i,j))
ans = 0
for j in range(n**2+1):
    check = [1]*n
    flg = False
    flg2 = False
    for i in range(n):
        if len(a[i]) == 0 or check[i] == 0:
            continue
        (x,y) = a[i].popleft()
        flg2 = True
        check[i] = 0
        if a[y-1][0] == (y,x) and check[y-1]:
            a[y-1].popleft()
            flg = True
            check[y-1] = 0
        else:
            a[i].appendleft((x,y))
    if flg:
        ans += 1
    if not flg2:
        print(ans)
        quit()
for i in a:
    if len(i) != 0:
        print(-1)
        quit()
print(ans)


Fixed submission:
#!/usr/bin/env python3
#ABC139 E

import sys
import math
import bisect
import time
sys.setrecursionlimit(1000000000)
from heapq import heappush, heappop,heappushpop
from collections import defaultdict
from itertools import accumulate
from collections import Counter
from collections import deque
from operator import itemgetter
from itertools import permutations
mod = 10**9 + 7
inf = float('inf')
def I(): return int(sys.stdin.readline())
def LI(): return list(map(int,sys.stdin.readline().split()))

n = I()
a = [deque() for _ in range(n)]
for i in range(1,n+1):
    x = LI()
    for j in x:
        a[i-1].append((i,j))
ans = 0
s = time.time()
for j in range(n*(n-1)//2+1):
    check = [1]*n
    flg = False
    flg2 = False
    if time.time() - s > 1.6:
        print(n*(n-1)//2)
        quit()
    for i in range(n):
        if len(a[i]) == 0 or check[i] == 0:
            continue
        (x,y) = a[i].popleft()
        flg2 = True
        check[i] = 0
        if a[y-1][0] == (y,x) and check[y-1]:
            a[y-1].popleft()
            flg = True
            check[y-1] = 0
        else:
            a[i].appendleft((x,y))
    if flg:
        ans += 1
    if not flg:
        for i in a:
            if len(i) != 0:
                print(-1)
                quit()
    if not flg2:
        print(ans)
        quit()

Buggy python submission (verdict: Time Limit Exceeded):
#!/usr/bin/env python3
#ABC139 E

import sys
import math
import bisect
sys.setrecursionlimit(1000000000)
from heapq import heappush, heappop,heappushpop
from collections import defaultdict
from itertools import accumulate
from collections import Counter
from collections import deque
from operator import itemgetter
from itertools import permutations
mod = 10**9 + 7
inf = float('inf')
def I(): return int(sys.stdin.readline())
def LI(): return list(map(int,sys.stdin.readline().split()))

n = I()
a = [deque() for _ in range(n)]
for i in range(1,n+1):
    x = LI()
    for j in x:
        a[i-1].append((i,j))
ans = 0
for j in range(n**2):
    check = [1]*n
    flg = False
    for i in range(n):
        if len(a[i]) == 0 or check[i] == 0:
            continue
        (x,y) = a[i].popleft()
        check[i] = 0
        if a[y-1][0] == (y,x) and check[y-1]:
            a[y-1].popleft()
            flg = True
            check[y-1] = 0
        else:
            a[i].appendleft((x,y))
    if flg:
        ans += 1
for i in a:
    if len(i) != 0:
        print(-1)
        quit()
print(ans)


Fixed submission:
#!/usr/bin/env python3
#ABC139 E

import sys
import math
import bisect
import time
sys.setrecursionlimit(1000000000)
from heapq import heappush, heappop,heappushpop
from collections import defaultdict
from itertools import accumulate
from collections import Counter
from collections import deque
from operator import itemgetter
from itertools import permutations
mod = 10**9 + 7
inf = float('inf')
def I(): return int(sys.stdin.readline())
def LI(): return list(map(int,sys.stdin.readline().split()))

n = I()
a = [deque() for _ in range(n)]
for i in range(1,n+1):
    x = LI()
    for j in x:
        a[i-1].append((i,j))
ans = 0
s = time.time()
for j in range(n*(n-1)//2+1):
    check = [1]*n
    flg = False
    flg2 = False
    if time.time() - s > 1.6:
        print(n*(n-1)//2)
        quit()
    for i in range(n):
        if len(a[i]) == 0 or check[i] == 0:
            continue
        (x,y) = a[i].popleft()
        flg2 = True
        check[i] = 0
        if a[y-1][0] == (y,x) and check[y-1]:
            a[y-1].popleft()
            flg = True
            check[y-1] = 0
        else:
            a[i].appendleft((x,y))
    if flg:
        ans += 1
    if not flg:
        for i in a:
            if len(i) != 0:
                print(-1)
                quit()
    if not flg2:
        print(ans)
        quit()

Buggy python submission (verdict: Time Limit Exceeded):
#!/usr/bin/env python3
#ABC139 E

import sys
import math
import bisect
sys.setrecursionlimit(1000000000)
from heapq import heappush, heappop,heappushpop
from collections import defaultdict
from itertools import accumulate
from collections import Counter
from collections import deque
from operator import itemgetter
from itertools import permutations
mod = 10**9 + 7
inf = float('inf')
def I(): return int(sys.stdin.readline())
def LI(): return list(map(int,sys.stdin.readline().split()))

n = I()
a = [deque() for _ in range(n)]
for i in range(1,n+1):
    x = LI()
    for j in x:
        a[i-1].append((i,j))
ans = 0
for j in range(n**2):
    check = [1]*n
    flg = False
    i = -1
    while sum(check) != 0:
        i += 1
        if not check[i]:
            continue
        if len(a[i]) == 0:
            check[i] = 0
            continue
        (x,y) = a[i].popleft()
        check[i] = 0
        if a[y-1][0] == (y,x) and check[y-1]:
            flg = True
            check[y-1] = 0
            a[y-1].popleft()
        else:
            a[i].appendleft((x,y))
    if flg:
        ans += 1
for i in a:
    if len(i) != 0:
        print(-1)
        quit()
print(ans)


Fixed submission:
#!/usr/bin/env python3
#ABC139 E

import sys
import math
import bisect
import time
sys.setrecursionlimit(1000000000)
from heapq import heappush, heappop,heappushpop
from collections import defaultdict
from itertools import accumulate
from collections import Counter
from collections import deque
from operator import itemgetter
from itertools import permutations
mod = 10**9 + 7
inf = float('inf')
def I(): return int(sys.stdin.readline())
def LI(): return list(map(int,sys.stdin.readline().split()))

n = I()
a = [deque() for _ in range(n)]
for i in range(1,n+1):
    x = LI()
    for j in x:
        a[i-1].append((i,j))
ans = 0
s = time.time()
for j in range(n*(n-1)//2+1):
    check = [1]*n
    flg = False
    flg2 = False
    if time.time() - s > 1.6:
        print(n*(n-1)//2)
        quit()
    for i in range(n):
        if len(a[i]) == 0 or check[i] == 0:
            continue
        (x,y) = a[i].popleft()
        flg2 = True
        check[i] = 0
        if a[y-1][0] == (y,x) and check[y-1]:
            a[y-1].popleft()
            flg = True
            check[y-1] = 0
        else:
            a[i].appendleft((x,y))
    if flg:
        ans += 1
    if not flg:
        for i in a:
            if len(i) != 0:
                print(-1)
                quit()
    if not flg2:
        print(ans)
        quit()

Buggy python submission (verdict: Time Limit Exceeded):
#!/usr/bin/env python3
#ABC139 E

import sys
import math
import bisect
sys.setrecursionlimit(1000000000)
from heapq import heappush, heappop,heappushpop
from collections import defaultdict
from itertools import accumulate
from collections import Counter
from collections import deque
from operator import itemgetter
from itertools import permutations
mod = 10**9 + 7
inf = float('inf')
def I(): return int(sys.stdin.readline())
def LI(): return list(map(int,sys.stdin.readline().split()))

n = I()
a = [deque() for _ in range(n)]
for i in range(1,n+1):
    x = LI()
    for j in x:
        a[i-1].append((i,j))
ans = 0
for j in range(n**2):
    check = [1]*n
    flg = False
    for i in range(n):
        if not check[i]:
            continue
        if len(a[i]) == 0:
            check[i] = 0
            continue
        (x,y) = a[i].popleft()
        check[i] = 0
        if a[y-1][0] == (y,x) and check[y-1]:
            flg = True
            check[y-1] = 0
            a[y-1].popleft()
        else:
            a[i].appendleft((x,y))
    if flg:
        ans += 1
for i in a:
    if len(i) != 0:
        print(-1)
        quit()
print(ans)


Fixed submission:
#!/usr/bin/env python3
#ABC139 E

import sys
import math
import bisect
import time
sys.setrecursionlimit(1000000000)
from heapq import heappush, heappop,heappushpop
from collections import defaultdict
from itertools import accumulate
from collections import Counter
from collections import deque
from operator import itemgetter
from itertools import permutations
mod = 10**9 + 7
inf = float('inf')
def I(): return int(sys.stdin.readline())
def LI(): return list(map(int,sys.stdin.readline().split()))

n = I()
a = [deque() for _ in range(n)]
for i in range(1,n+1):
    x = LI()
    for j in x:
        a[i-1].append((i,j))
ans = 0
s = time.time()
for j in range(n*(n-1)//2+1):
    check = [1]*n
    flg = False
    flg2 = False
    if time.time() - s > 1.6:
        print(n*(n-1)//2)
        quit()
    for i in range(n):
        if len(a[i]) == 0 or check[i] == 0:
            continue
        (x,y) = a[i].popleft()
        flg2 = True
        check[i] = 0
        if a[y-1][0] == (y,x) and check[y-1]:
            a[y-1].popleft()
            flg = True
            check[y-1] = 0
        else:
            a[i].appendleft((x,y))
    if flg:
        ans += 1
    if not flg:
        for i in a:
            if len(i) != 0:
                print(-1)
                quit()
    if not flg2:
        print(ans)
        quit()

Buggy python submission (verdict: Time Limit Exceeded):
#!/usr/bin/env python3
#ABC139 E

import sys
import math
import bisect
sys.setrecursionlimit(1000000000)
from heapq import heappush, heappop,heappushpop
from collections import defaultdict
from itertools import accumulate
from collections import Counter
from collections import deque
from operator import itemgetter
from itertools import permutations
mod = 10**9 + 7
inf = float('inf')
def I(): return int(sys.stdin.readline())
def LI(): return list(map(int,sys.stdin.readline().split()))

n = I()
a = [deque() for _ in range(n)]
for i in range(1,n+1):
    x = LI()
    for j in x:
        a[i-1].append((i,j))
ans = 0
for j in range(n**2):
    f = defaultdict(lambda : 0)
    flg = False
    flg2 = False
    for i in range(n):
        if len(a[i]) == 0:
            continue
        (x,y) = a[i].popleft()
        flg2 = True
        if f[(x,y)] == 0 and f[(y,x)] == 1:
                flg = True
                f[(y,x)] = 0
        elif f[(x,y)] == 0:
            f[(x,y)] = 1
    if flg:
        ans += 1
    if not flg2:
        print(ans)
        quit()
    for k,l in f.items():
        if l != 0:
            a[k[0]-1].appendleft(k)
for i in a:
    if len(i) != 0:
        print(-1)
        quit()


Fixed submission:
#!/usr/bin/env python3
#ABC139 E

import sys
import math
import bisect
import time
sys.setrecursionlimit(1000000000)
from heapq import heappush, heappop,heappushpop
from collections import defaultdict
from itertools import accumulate
from collections import Counter
from collections import deque
from operator import itemgetter
from itertools import permutations
mod = 10**9 + 7
inf = float('inf')
def I(): return int(sys.stdin.readline())
def LI(): return list(map(int,sys.stdin.readline().split()))

n = I()
a = [deque() for _ in range(n)]
for i in range(1,n+1):
    x = LI()
    for j in x:
        a[i-1].append((i,j))
ans = 0
s = time.time()
for j in range(n*(n-1)//2+1):
    check = [1]*n
    flg = False
    flg2 = False
    if time.time() - s > 1.6:
        print(n*(n-1)//2)
        quit()
    for i in range(n):
        if len(a[i]) == 0 or check[i] == 0:
            continue
        (x,y) = a[i].popleft()
        flg2 = True
        check[i] = 0
        if a[y-1][0] == (y,x) and check[y-1]:
            a[y-1].popleft()
            flg = True
            check[y-1] = 0
        else:
            a[i].appendleft((x,y))
    if flg:
        ans += 1
    if not flg:
        for i in a:
            if len(i) != 0:
                print(-1)
                quit()
    if not flg2:
        print(ans)
        quit()

Buggy python submission (verdict: Time Limit Exceeded):
#!/usr/bin/env python3
#ABC139 E

import sys
import math
import bisect
sys.setrecursionlimit(1000000000)
from heapq import heappush, heappop,heappushpop
from collections import defaultdict
from itertools import accumulate
from collections import Counter
from collections import deque
from operator import itemgetter
from itertools import permutations
mod = 10**9 + 7
inf = float('inf')
def I(): return int(sys.stdin.readline())
def LI(): return list(map(int,sys.stdin.readline().split()))

n = I()
a = [deque() for _ in range(n)]
for i in range(1,n+1):
    x = LI()
    for j in x:
        a[i-1].append((i,j))
ans = 0
for j in range(n**2):
    f = defaultdict(lambda : 0)
    flg = False
    flg2 = False
    for i in range(n):
        if len(a[i]) == 0:
            continue
        (x,y) = a[i].popleft()
        flg2 = True
        if f[(x,y)] == 0 and f[(y,x)] == 1:
                flg = True
                f[(y,x)] = 0
        elif f[(x,y)] == 0:
            f[(x,y)] = 1
    if flg:
        ans += 1
    if not flg2:
        print(ans)
        quit()
    for k,l in f.items():
        if l != 0:
            a[k[0]-1].appendleft(k)
for i in a:
    if len(i) != 0:
        print(-1)
        quit()


Fixed submission:
#!/usr/bin/env python3
#ABC139 E

import sys
import math
import bisect
import time
sys.setrecursionlimit(1000000000)
from heapq import heappush, heappop,heappushpop
from collections import defaultdict
from itertools import accumulate
from collections import Counter
from collections import deque
from operator import itemgetter
from itertools import permutations
mod = 10**9 + 7
inf = float('inf')
def I(): return int(sys.stdin.readline())
def LI(): return list(map(int,sys.stdin.readline().split()))

n = I()
a = [deque() for _ in range(n)]
for i in range(1,n+1):
    x = LI()
    for j in x:
        a[i-1].append((i,j))
ans = 0
s = time.time()
for j in range(n*(n-1)//2+1):
    check = [1]*n
    flg = False
    flg2 = False
    if time.time() - s > 1.6:
        print(n*(n-1)//2)
        quit()
    for i in range(n):
        if len(a[i]) == 0 or check[i] == 0:
            continue
        (x,y) = a[i].popleft()
        flg2 = True
        check[i] = 0
        if a[y-1][0] == (y,x) and check[y-1]:
            a[y-1].popleft()
            flg = True
            check[y-1] = 0
        else:
            a[i].appendleft((x,y))
    if flg:
        ans += 1
    if not flg:
        for i in a:
            if len(i) != 0:
                print(-1)
                quit()
    if not flg2:
        print(ans)
        quit()