Buggy python submission (verdict: Time Limit Exceeded):
import sys
input = sys.stdin.readline
N = int(input())
A = []
for i in range(N):
    A.append(list(map(int, input().split())))
index = [0]*(N+1)
ans = -2
for k in range(30000):
    today = set()
    flag = 0
    for j in range(N):
        if j+1 in today:
            continue
        if index[j+1] >= N-1:
            continue
        #print(j, index[j+1])
        opponent = A[j][index[j+1]]
        if A[opponent-1][index[opponent]] == j+1:
            if opponent not in today:
                index[opponent] += 1
                index[j+1] += 1
                today.add(opponent)
                today.add(j+1)
                flag = 1
    if flag == 0:
        if sum(index) == N*(N-1):
            ans = k
            break
        else:
            ans = -1
            break
    #print(index)

if ans == -2:
    print(N*(N-1)//2)
else:
    print(ans)


Fixed submission:
import sys
input = sys.stdin.readline
N = int(input())
A = []
for i in range(N):
    A.append(list(map(int, input().split())))
index = [0]*(N+1)
ans = -2
for k in range(10000):
    today = set()
    flag = 0
    for j in range(N):
        if j+1 in today:
            continue
        if index[j+1] >= N-1:
            continue
        #print(j, index[j+1])
        opponent = A[j][index[j+1]]
        if A[opponent-1][index[opponent]] == j+1:
            if opponent not in today:
                index[opponent] += 1
                index[j+1] += 1
                today.add(opponent)
                today.add(j+1)
                flag = 1
    if flag == 0:
        if sum(index) == N*(N-1):
            ans = k
            break
        else:
            ans = -1
            break
    #print(index)

if ans == -2:
    print(N*(N-1)//2)
else:
    print(ans)

Buggy python submission (verdict: Runtime Error):
import sys
input = sys.stdin.readline
N = int(input())
A = []
for i in range(N):
    A.append(list(map(int, input().split())))
index = [0]*(N+1)

for k in range(30000):
    today = set()
    flag = 0
    for j in range(N):
        if j+1 in today:
            continue
        if index[j+1] >= N-1:
            continue
        #print(j, index[j+1])
        opponent = A[j][index[j+1]]
        if A[opponent-1][index[opponent]] == j+1:
            if opponent not in today:
                index[opponent] += 1
                index[j+1] += 1
                today.add(opponent)
                today.add(j+1)
                flag = 1
    if flag == 0:
        if sum(index) == N*(N-1):
            ans = k
            break
        else:
            ans = -1
            break
    #print(index)

print(ans)


Fixed submission:
import sys
input = sys.stdin.readline
N = int(input())
A = []
for i in range(N):
    A.append(list(map(int, input().split())))
index = [0]*(N+1)
ans = -2
for k in range(10000):
    today = set()
    flag = 0
    for j in range(N):
        if j+1 in today:
            continue
        if index[j+1] >= N-1:
            continue
        #print(j, index[j+1])
        opponent = A[j][index[j+1]]
        if A[opponent-1][index[opponent]] == j+1:
            if opponent not in today:
                index[opponent] += 1
                index[j+1] += 1
                today.add(opponent)
                today.add(j+1)
                flag = 1
    if flag == 0:
        if sum(index) == N*(N-1):
            ans = k
            break
        else:
            ans = -1
            break
    #print(index)

if ans == -2:
    print(N*(N-1)//2)
else:
    print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
import sys
input = sys.stdin.readline
N = int(input())
A = []
for i in range(N):
    A.append(list(map(int, input().split())))
index = [0]*(N+1)

for k in range(600000):
    today = set()
    flag = 0
    for j in range(N):
        if j+1 in today:
            continue
        if index[j+1] >= N-1:
            continue
        #print(j, index[j+1])
        opponent = A[j][index[j+1]]
        if A[opponent-1][index[opponent]] == j+1:
            if opponent not in today:
                index[opponent] += 1
                index[j+1] += 1
                today.add(opponent)
                today.add(j+1)
                flag = 1
    if flag == 0:
        if sum(index) == N*(N-1):
            ans = k
            break
        else:
            ans = -1
            break
    #print(index)

print(ans)


Fixed submission:
import sys
input = sys.stdin.readline
N = int(input())
A = []
for i in range(N):
    A.append(list(map(int, input().split())))
index = [0]*(N+1)
ans = -2
for k in range(10000):
    today = set()
    flag = 0
    for j in range(N):
        if j+1 in today:
            continue
        if index[j+1] >= N-1:
            continue
        #print(j, index[j+1])
        opponent = A[j][index[j+1]]
        if A[opponent-1][index[opponent]] == j+1:
            if opponent not in today:
                index[opponent] += 1
                index[j+1] += 1
                today.add(opponent)
                today.add(j+1)
                flag = 1
    if flag == 0:
        if sum(index) == N*(N-1):
            ans = k
            break
        else:
            ans = -1
            break
    #print(index)

if ans == -2:
    print(N*(N-1)//2)
else:
    print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
import sys
input = sys.stdin.readline
N = int(input())
A = []
for i in range(N):
    A.append(list(map(int, input().split())))
index = [0]*(N+1)

for k in range(600000):
    today = [True]*(N+1)
    flag = 0
    for j in range(N):
        if not today[j+1]:
            continue
        if index[j+1] >= N-1:
            continue
        opponent = A[j][index[j+1]]
        if A[opponent-1][index[opponent]] == j+1:
            if today[opponent]:
                index[opponent] += 1
                index[j+1] += 1
                today[opponent] = False
                today[j+1] = False
                flag = 1
    if flag == 0:
        if sum(index) == N*(N-1):
            ans = k
            break
        else:
            ans = -1
            break

print(ans)


Fixed submission:
import sys
input = sys.stdin.readline
N = int(input())
A = []
for i in range(N):
    A.append(list(map(int, input().split())))
index = [0]*(N+1)
ans = -2
for k in range(10000):
    today = set()
    flag = 0
    for j in range(N):
        if j+1 in today:
            continue
        if index[j+1] >= N-1:
            continue
        #print(j, index[j+1])
        opponent = A[j][index[j+1]]
        if A[opponent-1][index[opponent]] == j+1:
            if opponent not in today:
                index[opponent] += 1
                index[j+1] += 1
                today.add(opponent)
                today.add(j+1)
                flag = 1
    if flag == 0:
        if sum(index) == N*(N-1):
            ans = k
            break
        else:
            ans = -1
            break
    #print(index)

if ans == -2:
    print(N*(N-1)//2)
else:
    print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
import sys
input = sys.stdin.readline
N = int(input())
A = [list(map(int, input().split())) for i in range(N)]
index = [0]*(N+1)

ans = -1
for _ in range(600000):
    today = [True]*(N+1)
    flag = 0
    for j in range(N):
        if not today[j+1]:
            continue
        if index[j+1] >= N-1:
            continue
        #print(j, index[j+1])
        opponent = A[j][index[j+1]]
        if today[j+1] and today[opponent] and A[opponent-1][index[opponent]] == j+1:
            index[opponent] += 1
            index[j+1] += 1
            today[opponent] = False
            today[j+1] = False
            flag = 1
    ans += 1
    if flag == 0:
        if sum(index) == N*(N-1):
            break
        else:
            ans = -1
            break
    #print(index)

print(ans)


Fixed submission:
import sys
input = sys.stdin.readline
N = int(input())
A = []
for i in range(N):
    A.append(list(map(int, input().split())))
index = [0]*(N+1)
ans = -2
for k in range(10000):
    today = set()
    flag = 0
    for j in range(N):
        if j+1 in today:
            continue
        if index[j+1] >= N-1:
            continue
        #print(j, index[j+1])
        opponent = A[j][index[j+1]]
        if A[opponent-1][index[opponent]] == j+1:
            if opponent not in today:
                index[opponent] += 1
                index[j+1] += 1
                today.add(opponent)
                today.add(j+1)
                flag = 1
    if flag == 0:
        if sum(index) == N*(N-1):
            ans = k
            break
        else:
            ans = -1
            break
    #print(index)

if ans == -2:
    print(N*(N-1)//2)
else:
    print(ans)