Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
A = [int(i) for i in input().split()]
ans = 0
if N % 2 != 0:
    num_list = [int(i) for i in range(2, N, 2)]
    for num in num_list:
        if A.count(num) != 2:
            break
    else:
        if A.count(0) == 1:
            ans = (2 ** (N // 2)) % (10**7 + 7)

else:
    num_list = [int(i) for i in range(1, N, 2)]
    for num in num_list:
        if A.count(num) != 2:
            break
    else:
        ans = 2 ** (N // 2) % (10**7 + 7)

print(ans)


Fixed submission:
N = int(input())
A = list(map(int, input().split()))
ans = 1
if N % 2 == 0:
    if len(A) != 2*len(set(A)):
        ans = 0
else:
    if A.count(0) == 1:
        A.remove(0)
        if len(A) != 2*len(set(A)):
            ans = 0
    else:
        ans = 0
if ans == 0:
    print(0)
else:
    print((2**(N//2))%(10**9+7))

Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
A = [int(i) for i in input().split()]
ans = 0
if N % 2 != 0:
    num_list = [int(i) for i in range(2, N, 2)]
    for num in num_list:
        if A.count(num) != 2:
            break
    else:
        if A.count(0) == 1:
            ans = 2 ** (N // 2)

else:
    num_list = [int(i) for i in range(1, N, 2)]
    for num in num_list:
        if A.count(num) != 2:
            break
    else:
        ans = 2 ** (N // 2)

print(ans)


Fixed submission:
N = int(input())
A = list(map(int, input().split()))
ans = 1
if N % 2 == 0:
    if len(A) != 2*len(set(A)):
        ans = 0
else:
    if A.count(0) == 1:
        A.remove(0)
        if len(A) != 2*len(set(A)):
            ans = 0
    else:
        ans = 0
if ans == 0:
    print(0)
else:
    print((2**(N//2))%(10**9+7))

Buggy python submission (verdict: Runtime Error):
import sys

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

if N % 2 != 0:
    if A[0] == 0:
        a = A[1:]
        j = 1
        k = 0
        for i in range(0, N//2 + 1, 2):
            if a[k] == a[k+1] == 2*j:
                j += 1
                k += 2
            else:
                print(0)
                sys.exit()
        print((2**(N//2)) % (10**9+7))
        
    else:
        print(0)
else:
    j = 1
    k = 0
    for i in range(0, N//2 + 1, 2):
        if A[k] == A[k+1] == 2*j -1:
            j += 1
            k += 2
        else:
            print(0)
            sys.exit()
    print((2**(N//2)) % (10**9+7))

Fixed submission:
N = int(input())
A = list(map(int, input().split()))
ans = 1
if N % 2 == 0:
    if len(A) != 2*len(set(A)):
        ans = 0
else:
    if A.count(0) == 1:
        A.remove(0)
        if len(A) != 2*len(set(A)):
            ans = 0
    else:
        ans = 0
if ans == 0:
    print(0)
else:
    print((2**(N//2))%(10**9+7))

Buggy python submission (verdict: Runtime Error):
import sys

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

if N % 2 != 0:
    if A[0] == 0:
        a = A[1:]
        j = 1
        for i in range(0, N//2 + 1, 2):
            if a[i] == a[i+1] == 2*j:
                j += 1
            else:
                print(0)
                sys.exit()
        print((2**(N//2)) % (10**9+7))
        
    else:
        print(0)
else:
    j = 1
    k = 0
    for i in range(0, N//2 + 1, 2):
        if A[k] == A[k+1] == 2*j -1:
            j += 1
            k += 2
        else:
            print(0)
            sys.exit()
    print((2**(N//2)) % (10**9+7))

Fixed submission:
N = int(input())
A = list(map(int, input().split()))
ans = 1
if N % 2 == 0:
    if len(A) != 2*len(set(A)):
        ans = 0
else:
    if A.count(0) == 1:
        A.remove(0)
        if len(A) != 2*len(set(A)):
            ans = 0
    else:
        ans = 0
if ans == 0:
    print(0)
else:
    print((2**(N//2))%(10**9+7))

Buggy python submission (verdict: Runtime Error):
import sys

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

if N % 2 != 0:
    if A[0] == 0:
        a = A[1:]
        j = 1
        for i in range(0, N//2 + 1, 2):
            if a[i] == a[i+1] == 2*j:
                j += 1
            else:
                print(0)
                sys.exit()
        print((2**(N//2)) % (10**9+7))
        
    else:
        print(0)
else:
    j = 1
    for i in range(0, N//2+1, 2):
        if A[i] == A[i+i] == 2*j -1:
            j += 1
        else:
            print(0)
            sys.exit()
    print((2**(N//2)) % (10**9+7))

Fixed submission:
N = int(input())
A = list(map(int, input().split()))
ans = 1
if N % 2 == 0:
    if len(A) != 2*len(set(A)):
        ans = 0
else:
    if A.count(0) == 1:
        A.remove(0)
        if len(A) != 2*len(set(A)):
            ans = 0
    else:
        ans = 0
if ans == 0:
    print(0)
else:
    print((2**(N//2))%(10**9+7))

Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
A = list(map(int, input().split()))
ans = 1
if N % 2 == 0:
    
    for i in list(range(1, N, 2)):
        if A.count(i) != 2:
            ans = 0
            break
            
else:
    if A.count(0) == 1:
        for i in list(range(2, N, 2)):
            if A.count(i) != 2:
                ans = 0
                break
    else:
        ans = 0

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

Fixed submission:
N = int(input())
A = list(map(int, input().split()))
ans = 1
if N % 2 == 0:
    if len(A) != 2*len(set(A)):
        ans = 0
else:
    if A.count(0) == 1:
        A.remove(0)
        if len(A) != 2*len(set(A)):
            ans = 0
    else:
        ans = 0
if ans == 0:
    print(0)
else:
    print((2**(N//2))%(10**9+7))

Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
A = list(map(int, input().split()))
ans = 0
if N % 2 == 0:
    
    for i in list(range(1, N, 2)):
        if A.count(i) == 2:
            ans += 1
        else:
            break
else:
    if A.count(0) == 1:
        
        for i in list(range(0, N, 2)):
            if 1 <= A.count(i) <=2:
                ans +=1
            else:
                break
    else:
        ans = 0

if ans != 0:
    if N%2 == 0:
        print((2**ans)%(10**9+7))
    else:
        print((2**(ans-1))%(10**9+7))
else:
    print(0)

Fixed submission:
N = int(input())
A = list(map(int, input().split()))
ans = 1
if N % 2 == 0:
    if len(A) != 2*len(set(A)):
        ans = 0
else:
    if A.count(0) == 1:
        A.remove(0)
        if len(A) != 2*len(set(A)):
            ans = 0
    else:
        ans = 0
if ans == 0:
    print(0)
else:
    print((2**(N//2))%(10**9+7))

Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
A = list(map(int, input().split()))
ans = 1
if N % 2 == 0:
    
    for i in list(range(1, N, 2)):
        if 1 <= A.count(i) <= 2:
            ans = (ans*A.count(i))%(10**9+7)
        else:
            ans = 0
            break
else:
    if A.count(0) == 1:
        
        for i in list(range(0, N, 2)):
            if 1 <= A.count(i) <=2:
                ans = (ans*A.count(i))%(10**9+7)
            else:
                ans = 0
                break
    else:
        ans = 0

print(ans)

Fixed submission:
N = int(input())
A = list(map(int, input().split()))
ans = 1
if N % 2 == 0:
    if len(A) != 2*len(set(A)):
        ans = 0
else:
    if A.count(0) == 1:
        A.remove(0)
        if len(A) != 2*len(set(A)):
            ans = 0
    else:
        ans = 0
if ans == 0:
    print(0)
else:
    print((2**(N//2))%(10**9+7))

Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
A = list(map(int, input().split()))
ans = 1
if N % 2 == 0:
    
    for i in list(range(1, N, 2)):
        if 1 <= A.count(i) <= 2:
            ans = ans*A.count(i)
        else:
            ans = 0
            break
else:
    if A.count(0) == 1:
        
        for i in list(range(0, N, 2)):
            if 1 <= A.count(i) <=2:
                ans = ans*A.count(i)
            else:
                ans = 0
                break
    else:
        ans = 0

print(ans)

Fixed submission:
N = int(input())
A = list(map(int, input().split()))
ans = 1
if N % 2 == 0:
    if len(A) != 2*len(set(A)):
        ans = 0
else:
    if A.count(0) == 1:
        A.remove(0)
        if len(A) != 2*len(set(A)):
            ans = 0
    else:
        ans = 0
if ans == 0:
    print(0)
else:
    print((2**(N//2))%(10**9+7))