Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
A = [int(i) for i in input().split()]

if N % 2:
    if A.count(0) != 1:
        flg = 0
    else:
        if all(A.count(i) == 2 for i in range(2, N, 2)):
            flg = 1
        else:
            flg = 0
else:
    if all(A.count(i) == 2 for i in range(1, N, 2)):
        flg = 1
    else:
        flg = 0

if flg:
    ans = 2 ** (N//2) % (10**9+7)
else:
    ans = 0

print(ans)


Fixed submission:
from collections import Counter

N = int(input())
A = [int(i) for i in input().split()]
c = Counter(A)

flg = 0
if N % 2:
    if c[0] != 1:
        flg = 1
    else:
        for i in range(2, N, 2):
            if c[i] != 2:
                flg = 1
                break
else:
    for i in range(1, N, 2):
        if c[i] != 2:
            flg = 1
            break

if flg:
    ans = 0
else:
    ans = 2 ** (N//2) % (10**9+7)

print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
A = [int(i) for i in input().split()]

if N % 2:
    if A.count(0) != 1:
        flg = 0
    else:
        if all(A.count(i) == 2 for i in range(2, N, 2)):
            flg = 1
        else:
            flg = 0
else:
    if all(A.count(i) == 2 for i in range(1, N, 2)):
        flg = 1
    else:
        flg = 0

if flg:
    ans = 1
    for i in range(N//2):
        ans *= 2
        ans %= 10**9 + 7
else:
    ans = 0

print(ans)


Fixed submission:
from collections import Counter

N = int(input())
A = [int(i) for i in input().split()]
c = Counter(A)

flg = 0
if N % 2:
    if c[0] != 1:
        flg = 1
    else:
        for i in range(2, N, 2):
            if c[i] != 2:
                flg = 1
                break
else:
    for i in range(1, N, 2):
        if c[i] != 2:
            flg = 1
            break

if flg:
    ans = 0
else:
    ans = 2 ** (N//2) % (10**9+7)

print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
A = [int(i) for i in input().split()]

if N % 2:
    if A.count(0) != 1:
        flg = 0
    else:
        if all(j % 2 == 0 for j in A):
            if all(A.count(i) == 2 for i in range(2, N, 2)):
                flg = 1
            else:
                flg = 0
        else:
            flg = 0
else:
    if all(j % 2 for j in A):
        if all(A.count(i) == 2 for i in range(1, N, 2)):
            flg = 1
        else:
            flg = 0
    else:
        flg = 0

if flg:
    ans = 1
    for i in range(N//2):
        ans *= 2
        ans %= 10**9 + 7
else:
    ans = 0

print(ans)


Fixed submission:
from collections import Counter

N = int(input())
A = [int(i) for i in input().split()]
c = Counter(A)

flg = 0
if N % 2:
    if c[0] != 1:
        flg = 1
    else:
        for i in range(2, N, 2):
            if c[i] != 2:
                flg = 1
                break
else:
    for i in range(1, N, 2):
        if c[i] != 2:
            flg = 1
            break

if flg:
    ans = 0
else:
    ans = 2 ** (N//2) % (10**9+7)

print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
A = [int(i) for i in input().split()]

if N % 2:
    if A.count(0) != 1:
        flg = 0
    else:
        if all(A.count(i) == 2 for i in range(2, N, 2)):
            if all(j % 2 == 0 for j in A):
                flg = 1
            else:
                flg = 0
        else:
            flg = 0
else:
    if all(A.count(i) == 2 for i in range(1, N, 2)):
        if all(j % 2 for j in A):
            flg = 1
        else:
            flg = 0
    else:
        flg = 0

print(2**(N//2) if flg else 0)


Fixed submission:
from collections import Counter

N = int(input())
A = [int(i) for i in input().split()]
c = Counter(A)

flg = 0
if N % 2:
    if c[0] != 1:
        flg = 1
    else:
        for i in range(2, N, 2):
            if c[i] != 2:
                flg = 1
                break
else:
    for i in range(1, N, 2):
        if c[i] != 2:
            flg = 1
            break

if flg:
    ans = 0
else:
    ans = 2 ** (N//2) % (10**9+7)

print(ans)