Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
from collections import defaultdict
N = int(input())

def trans(x):
    return int(x)-1

A = deque()
for _ in range(N):
    A.append(deque(map(trans,input().split())))

Q = deque()

def check(i):
    if len(A[i]) == 0:
        return
    j = A[i][0]
    if len(A[j]) == 0:
        return
    if A[j][0] == i:
        if i > j:
            i, j = j, i
        Q.append([i, j])

def get_unique(q):
    r = deque()
    seen = defaultdict(int)
    for a in q:
        if seen[a[0]] == 0:
            seen[a[0]] = 1
            r.append(a)
    return r


for i in range(N):
    check(i)

ans = 0
while len(Q) > 0:
    ans += 1
    Q2 = get_unique(Q)
    Q = deque()
    for q in Q2:
        A[q[0]].popleft()
        A[q[1]].popleft()
    for q in Q2:
        check(q[0])
        check(q[1])

for i in range(N):
    if len(A[i]) > 0:
        print(-1)
        exit()

print(ans)

Fixed submission:
from collections import deque
N = int(input())

def trans(x):
    return int(x)-1

A = deque()
for _ in range(N):
    A.append(deque(map(trans,input().split())))

Q = set()

def check(i):
    if len(A[i]) == 0:
        return
    j = A[i][0]
    if len(A[j]) == 0:
        return
    if A[j][0] == i:
        if i > j:
            i, j = j, i
        Q.add((i, j))

for i in range(N):
    check(i)

ans = 0
while len(Q) > 0:
    ans += 1
    Q2 = Q.copy()
    Q = set()
    for q in Q2:
        A[q[0]].popleft()
        A[q[1]].popleft()
    for q in Q2:
        check(q[0])
        check(q[1])

for i in range(N):
    if len(A[i]) > 0:
        print(-1)
        exit()

print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
from collections import defaultdict
N = int(input())

def trans(x):
    return int(x)-1

A = deque()
for _ in range(N):
    A.append(deque(map(trans,input().split())))

Q = deque()

def check(i):
    if len(A[i]) == 0:
        return
    j = A[i][0]
    if len(A[j]) == 0:
        return
    if A[j][0] == i:
        if i > j:
            i, j = j, i
        Q.append([i, j])

def get_unique(q):
    r = deque()
    seen = defaultdict(int)
    for a in q:
        key = str(a[0]) + "-" + str(a[1])
        if seen[key] == 0:
            seen[key] = 1
            r.append(a)
    return r


for i in range(N):
    check(i)

ans = 0
while len(Q) > 0:
    ans += 1
    Q2 = get_unique(Q)
    Q = deque()
    for q in Q2:
        A[q[0]].popleft()
        A[q[1]].popleft()
    for q in Q2:
        check(q[0])
        check(q[1])

for i in range(N):
    if len(A[i]) > 0:
        print(-1)
        exit()

print(ans)

Fixed submission:
from collections import deque
N = int(input())

def trans(x):
    return int(x)-1

A = deque()
for _ in range(N):
    A.append(deque(map(trans,input().split())))

Q = set()

def check(i):
    if len(A[i]) == 0:
        return
    j = A[i][0]
    if len(A[j]) == 0:
        return
    if A[j][0] == i:
        if i > j:
            i, j = j, i
        Q.add((i, j))

for i in range(N):
    check(i)

ans = 0
while len(Q) > 0:
    ans += 1
    Q2 = Q.copy()
    Q = set()
    for q in Q2:
        A[q[0]].popleft()
        A[q[1]].popleft()
    for q in Q2:
        check(q[0])
        check(q[1])

for i in range(N):
    if len(A[i]) > 0:
        print(-1)
        exit()

print(ans)

Buggy python submission (verdict: Runtime Error):
from collections import deque
from collections import defaultdict
N = int(input())

def trans(x):
    return int(x)-1

A = deque()
for _ in range(N):
    A.append(deque(map(trans,input().split())))

Q = deque()

def check(i):
    if len(A[i]) == 0:
        return
    j = A[i][0]
    if len(A[j]) == 0:
        return
    if A[j][0] == i:
        if i > j:
            i, j = j, i
        Q.append([i, j])

for i in range(N):
    check(i)

ans = 0
while len(Q) > 0:
    ans += 1
    Q2 = Q.copy()
    qcheck = defaultdict(int)
    Q3 = []
    Q = deque()
    for q in Q2:
        key = str(q[0]) + "-" + str(q[1])
        if qcheck[key] == 0:
            A[q[0]].popleft()
            A[q[1]].popleft()
            qcheck[key] += 1
            Q3.append(q)
    for q in Q3:
        check(q[0])
        check(q[1])

for i in range(N):
    if len(A[i]) > 0:
        print(-1)
        exit()

print(ans)

Fixed submission:
from collections import deque
N = int(input())

def trans(x):
    return int(x)-1

A = deque()
for _ in range(N):
    A.append(deque(map(trans,input().split())))

Q = set()

def check(i):
    if len(A[i]) == 0:
        return
    j = A[i][0]
    if len(A[j]) == 0:
        return
    if A[j][0] == i:
        if i > j:
            i, j = j, i
        Q.add((i, j))

for i in range(N):
    check(i)

ans = 0
while len(Q) > 0:
    ans += 1
    Q2 = Q.copy()
    Q = set()
    for q in Q2:
        A[q[0]].popleft()
        A[q[1]].popleft()
    for q in Q2:
        check(q[0])
        check(q[1])

for i in range(N):
    if len(A[i]) > 0:
        print(-1)
        exit()

print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
N = int(input())

def trans(x):
    return int(x)-1

A = deque()
for _ in range(N):
    A.append(deque(map(trans,input().split())))

Q = deque()

def check(i):
    if len(A[i]) == 0:
        return
    j = A[i][0]
    if len(A[j]) == 0:
        return
    if A[j][0] == i:
        if i > j:
            i, j = j, i
        Q.append([i, j])

def get_unique(q):
    r = deque()
    seen = []
    for a in q:
        if a not in seen:
            seen.append(a)
            r.append(a)
    return r


for i in range(N):
    check(i)

ans = 0
while len(Q) > 0:
    ans += 1
    Q2 = get_unique(Q)
    Q = deque()
    for q in Q2:
        A[q[0]].popleft()
        A[q[1]].popleft()
    for q in Q2:
        check(q[0])
        check(q[1])

for i in range(N):
    if len(A[i]) > 0:
        print(-1)
        exit()

print(ans)

Fixed submission:
from collections import deque
N = int(input())

def trans(x):
    return int(x)-1

A = deque()
for _ in range(N):
    A.append(deque(map(trans,input().split())))

Q = set()

def check(i):
    if len(A[i]) == 0:
        return
    j = A[i][0]
    if len(A[j]) == 0:
        return
    if A[j][0] == i:
        if i > j:
            i, j = j, i
        Q.add((i, j))

for i in range(N):
    check(i)

ans = 0
while len(Q) > 0:
    ans += 1
    Q2 = Q.copy()
    Q = set()
    for q in Q2:
        A[q[0]].popleft()
        A[q[1]].popleft()
    for q in Q2:
        check(q[0])
        check(q[1])

for i in range(N):
    if len(A[i]) > 0:
        print(-1)
        exit()

print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
N = int(input())

def trans(x):
    return int(x)-1

A = deque()
for _ in range(N):
    A.append(deque(map(trans,input().split())))

Q = deque()

def check(i):
    if len(A[i]) == 0:
        return
    j = A[i][0]
    if len(A[j]) == 0:
        return
    if A[j][0] == i:
        if i > j:
            i, j = j, i
        Q.append([i, j])

def get_unique(q):
    r = deque()
    seen = []
    for a in q:
        if a not in seen:
            seen.append(a)
            r.append(a)
    return r


for i in range(N):
    check(i)

ans = 0
while len(Q) > 0:
    ans += 1
    Q2 = get_unique(Q)
    Q = deque()
    for q in Q2:
        A[q[0]].popleft()
        A[q[1]].popleft()
    for q in Q2:
        check(q[0])
        check(q[1])

for i in range(N):
    if len(A[i]) > 0:
        print(-1)
        exit()

print(ans)

Fixed submission:
from collections import deque
N = int(input())

def trans(x):
    return int(x)-1

A = deque()
for _ in range(N):
    A.append(deque(map(trans,input().split())))

Q = set()

def check(i):
    if len(A[i]) == 0:
        return
    j = A[i][0]
    if len(A[j]) == 0:
        return
    if A[j][0] == i:
        if i > j:
            i, j = j, i
        Q.add((i, j))

for i in range(N):
    check(i)

ans = 0
while len(Q) > 0:
    ans += 1
    Q2 = Q.copy()
    Q = set()
    for q in Q2:
        A[q[0]].popleft()
        A[q[1]].popleft()
    for q in Q2:
        check(q[0])
        check(q[1])

for i in range(N):
    if len(A[i]) > 0:
        print(-1)
        exit()

print(ans)