Buggy python submission (verdict: Runtime Error):
INFTY = 10**9+7
N = int(input())
A = list(map(int,input().split()))
C = {}
for i in range(N):
    if A[i] not in C:
        C[A[i]] = 0
    C[A[i]] += 1
if N%2==0:
    flag = 0
    for i in range(1,N,2):
        if C[i]==2:
            pass
        else:
            flag = 1
            break
else:
    flag = 0
    for i in range(2,N,2):
        if C[i]==2:
            pass
        else:
            flag = 1
            break
    if 0 not in C or C[0]!=1:
        flag = 1
if flag==0:
    cnt = 1
    for i in range(N//2):
        cnt = (cnt*2)%INFTY
else:
    cnt = 0
print(cnt)

Fixed submission:
INFTY = 10**9+7
N = int(input())
A = list(map(int,input().split()))
C = {}
for i in range(N):
    if A[i] not in C:
        C[A[i]] = 0
    C[A[i]] += 1
if N%2==0:
    flag = 0
    for i in range(1,N,2):
        if i in C and C[i]==2:
            pass
        else:
            flag = 1
            break
else:
    flag = 0
    for i in range(2,N,2):
        if i in C and C[i]==2:
            pass
        else:
            flag = 1
            break
    if 0 not in C or C[0]!=1:
        flag = 1
cnt = 0
if flag==0:
    cnt = 1
    for i in range(N//2):
        cnt = (cnt*2)%INFTY
print(cnt)

Buggy python submission (verdict: Runtime Error):
INFTY = 10**9+7
N = int(input())
A = list(map(int,input().split()))
C = {}
for i in range(N):
    if A[i] not in C:
        C[A[i]] = 0
    C[A[i]] += 1
if N%2==0:
    flag = 0
    for i in range(1,N,2):
        if C[i]==2:
            pass
        else:
            flag = 1
            break
else:
    flag = 0
    for i in range(2,N,2):
        if C[i]==2:
            pass
        else:
            flag = 1
            break
    if C[0]!=1:
        flag = 1
if flag==0:
    cnt = 1
    for i in range(N//2):
        cnt = (cnt*2)%INFTY
else:
    cnt = 0
print(cnt)

Fixed submission:
INFTY = 10**9+7
N = int(input())
A = list(map(int,input().split()))
C = {}
for i in range(N):
    if A[i] not in C:
        C[A[i]] = 0
    C[A[i]] += 1
if N%2==0:
    flag = 0
    for i in range(1,N,2):
        if i in C and C[i]==2:
            pass
        else:
            flag = 1
            break
else:
    flag = 0
    for i in range(2,N,2):
        if i in C and C[i]==2:
            pass
        else:
            flag = 1
            break
    if 0 not in C or C[0]!=1:
        flag = 1
cnt = 0
if flag==0:
    cnt = 1
    for i in range(N//2):
        cnt = (cnt*2)%INFTY
print(cnt)

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

Fixed submission:
INFTY = 10**9+7
N = int(input())
A = list(map(int,input().split()))
C = {}
for i in range(N):
    if A[i] not in C:
        C[A[i]] = 0
    C[A[i]] += 1
if N%2==0:
    flag = 0
    for i in range(1,N,2):
        if i in C and C[i]==2:
            pass
        else:
            flag = 1
            break
else:
    flag = 0
    for i in range(2,N,2):
        if i in C and C[i]==2:
            pass
        else:
            flag = 1
            break
    if 0 not in C or C[0]!=1:
        flag = 1
cnt = 0
if flag==0:
    cnt = 1
    for i in range(N//2):
        cnt = (cnt*2)%INFTY
print(cnt)