Buggy python submission (verdict: Runtime Error):
from collections import Counter
n = int(input())
ns = list(map(int, input().split()))
rslt = 0
a = 10 ** 9 + 7
cnt = Counter(ns)
if n % 2 == 0:
    for i in range(1, n, 2):
        if cnt[i] != 2:
            print(0)
            exit()
    rslt = pow(2, n // 2, a)
else:
    for i in range(2, n, 2):
        if cnt[i] != 2:
            print(0)
            exit()
    if c[0] == 1:
        rslt = pow(2, n // 2, a)
print(rslt)

Fixed submission:
from collections import Counter
n = int(input())
ns = list(map(int, input().split()))
rslt = 0
a = 10 ** 9 + 7
cnt = Counter(ns)
if n % 2 == 0:
    for i in range(1, n, 2):
        if cnt[i] != 2:
            print(0)
            exit()
    rslt = pow(2, n // 2, a)
else:
    for i in range(2, n, 2):
        if cnt[i] != 2:
            print(0)
            exit()
    if cnt[0] == 1:
        rslt = pow(2, n // 2, a)
print(rslt)

Buggy python submission (verdict: Runtime Error):
from collections import Counter
n = int(input())
ns = list(map(int, input().split()))
rslt = 0
a = 10 ** 9 + 7
cnt = Counter(ns)
if n % 2 == 0:
    for i in range(2, n, 2):
        if cnt[i] != 2:
            print(0)
            exit()
    rslt = pow(2, n // 2, a)
else:
    for i in range(1, n, 2):
        if cnt[i] != 2:
            print(0)
            exit()
    if c[0] == 1:
        rslt = pow(2, n // 2, a)
print(rslt)

Fixed submission:
from collections import Counter
n = int(input())
ns = list(map(int, input().split()))
rslt = 0
a = 10 ** 9 + 7
cnt = Counter(ns)
if n % 2 == 0:
    for i in range(1, n, 2):
        if cnt[i] != 2:
            print(0)
            exit()
    rslt = pow(2, n // 2, a)
else:
    for i in range(2, n, 2):
        if cnt[i] != 2:
            print(0)
            exit()
    if cnt[0] == 1:
        rslt = pow(2, n // 2, a)
print(rslt)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import Counter
n = int(input())
dic = Counter(list(map(int,input().split())))
rslt = 1
a = 10**9 + 7
if n % 2 == 0:
    if dic != Counter(sum([[i,i] for i in range(1, n, 2)], [])):
        rslt = 0
    else:
        rslt = 2**(n//2) % a

else:
    if dic != Counter(abs(i) for i in range(-n+1, n, 2)):
        rslt = 0
    else:
        rslt = 2**(n//2) % a
            
print(rslt)

Fixed submission:
from collections import Counter
n = int(input())
ns = list(map(int, input().split()))
rslt = 0
a = 10 ** 9 + 7
cnt = Counter(ns)
if n % 2 == 0:
    for i in range(1, n, 2):
        if cnt[i] != 2:
            print(0)
            exit()
    rslt = pow(2, n // 2, a)
else:
    for i in range(2, n, 2):
        if cnt[i] != 2:
            print(0)
            exit()
    if cnt[0] == 1:
        rslt = pow(2, n // 2, a)
print(rslt)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import Counter
n = int(input())
dic = Counter(list(map(int,input().split())))
rslt = 1
r = 10**9 + 7
if n % 2 == 0:
    if dic != Counter(sum([[i,i] for i in range(1, n, 2)], [])):
        rslt = 0
    else:
        for _ in range(n//2):
            rslt = rslt * 2 % r
else:
    if dic != Counter(abs(i) for i in range(-n+1, n, 2)):
        rslt = 0
    else:
        for _ in range(n//2):
            rslt = rslt * 2 % r
print(rslt)

Fixed submission:
from collections import Counter
n = int(input())
ns = list(map(int, input().split()))
rslt = 0
a = 10 ** 9 + 7
cnt = Counter(ns)
if n % 2 == 0:
    for i in range(1, n, 2):
        if cnt[i] != 2:
            print(0)
            exit()
    rslt = pow(2, n // 2, a)
else:
    for i in range(2, n, 2):
        if cnt[i] != 2:
            print(0)
            exit()
    if cnt[0] == 1:
        rslt = pow(2, n // 2, a)
print(rslt)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import Counter
n = int(input())
dic = Counter(list(map(int,input().split())))
rslt = 1
if n % 2 == 0:
    if dic != Counter(sum([[i,i] for i in range(1, n, 2)], [])):
        rslt = 0
    else:
        for _ in range(n//2):
            rslt = rslt * 2 % (10**9+7)
else:
    if dic != Counter(abs(i) for i in range(-n+1, n, 2)):
        rslt = 0
    else:
        for _ in range(n//2):
            rslt = rslt * 2 % (10**9+7)
print(rslt)

Fixed submission:
from collections import Counter
n = int(input())
ns = list(map(int, input().split()))
rslt = 0
a = 10 ** 9 + 7
cnt = Counter(ns)
if n % 2 == 0:
    for i in range(1, n, 2):
        if cnt[i] != 2:
            print(0)
            exit()
    rslt = pow(2, n // 2, a)
else:
    for i in range(2, n, 2):
        if cnt[i] != 2:
            print(0)
            exit()
    if cnt[0] == 1:
        rslt = pow(2, n // 2, a)
print(rslt)