Buggy python submission (verdict: Runtime Error):
n = int(input())
A = list(map(int, input().split()))
mod=int(1e9+7)

memo={}
for a in A:
  memo[a]=memo.get(a,0)+1

answer=1
if n%2:
  if memo[0]!=1:
    print(0)
    exit()
  for i in range(1, (n+1)//2):
    if memo[2*i]!=2:
      print(0)
      exit()
    else:
      answer = 2*answer %mod
elif not n%2:
  for i in range(n//2):
    if memo[2*i+1]!=2:
      print(0)
      exit()
    else:
      answer = 2*answer %mod
      
print(answer)
      
    


Fixed submission:
n = int(input())
A = list(map(int, input().split()))
mod=int(1e9+7)

memo={i:0 for i in range(n)}
for a in A:
  memo[a]=memo.get(a,0)+1

answer=1
if n%2:
  if memo[0]!=1:
    print(0)
    exit()
  for i in range(1, (n+1)//2):
    if memo[2*i]!=2:
      print(0)
      exit()
    else:
      answer = 2*answer %mod
elif not n%2:
  for i in range(n//2):
    if memo[2*i+1]!=2:
      print(0)
      exit()
    else:
      answer = 2*answer %mod
      
print(answer)

Buggy python submission (verdict: Runtime Error):
N=int(input())
A=list(map(int, input().split()))

if N%2:
  A = A+ [0]

Adict={}
for a in A:
  Adict[a] = Adict.get(a, 0) +1
  
#print(Adict)

# 0,0,2,2,4,4  5   (i//2)*2 + 1- N%2 0,2,4
# 1,1,3,3,5,5  6

#print(range(1-N%2, N, 2))
#print(all([Adict[i]==2 for i in range(1-N%2, N, 2)]))

if all([Adict[i]==2 for i in range(1-N%2, N, 2)]):
  answer = 1
  for _ in range(N//2):
    answer = (answer * 2)%1000000007
  print(answer)
else:
  print(0)

Fixed submission:
n = int(input())
A = list(map(int, input().split()))
mod=int(1e9+7)

memo={i:0 for i in range(n)}
for a in A:
  memo[a]=memo.get(a,0)+1

answer=1
if n%2:
  if memo[0]!=1:
    print(0)
    exit()
  for i in range(1, (n+1)//2):
    if memo[2*i]!=2:
      print(0)
      exit()
    else:
      answer = 2*answer %mod
elif not n%2:
  for i in range(n//2):
    if memo[2*i+1]!=2:
      print(0)
      exit()
    else:
      answer = 2*answer %mod
      
print(answer)

Buggy python submission (verdict: Runtime Error):
N=int(input())
A=list(map(int, input().split()))

if N%2:
  A = A+ [0]
  
print(A)
  
Adict={}
for a in A:
  Adict[a] = Adict.get(a, 0) +1
  
#print(Adict)

# 0,0,2,2,4,4  5   (i//2)*2 + 1- N%2 0,2,4
# 1,1,3,3,5,5  6

#print(range(1-N%2, N, 2))
#print(all([Adict[i]==2 for i in range(1-N%2, N, 2)]))

if all([Adict[i]==2 for i in range(1-N%2, N, 2)]):
  answer = 1
  for _ in range(N//2):
    answer = (answer * 2)%1000000007
  print(answer)
else:
  print(0)

Fixed submission:
n = int(input())
A = list(map(int, input().split()))
mod=int(1e9+7)

memo={i:0 for i in range(n)}
for a in A:
  memo[a]=memo.get(a,0)+1

answer=1
if n%2:
  if memo[0]!=1:
    print(0)
    exit()
  for i in range(1, (n+1)//2):
    if memo[2*i]!=2:
      print(0)
      exit()
    else:
      answer = 2*answer %mod
elif not n%2:
  for i in range(n//2):
    if memo[2*i+1]!=2:
      print(0)
      exit()
    else:
      answer = 2*answer %mod
      
print(answer)

Buggy python submission (verdict: Runtime Error):
N=int(input())
A=list(map(int, input().split()))

if N%2:
  A = A+ [0]
  
Adict={}
for a in A:
  Adict[a] = Adict.get(a, 0) +1

# 0,0,2,2,4,4  5   (i//2)*2 + 1- N%2 0,2,4
# 1,1,3,3,5,5  6

if all([Adict[i]==2 for i in range(1-N%2, N, 2)]):
  print(2**(N//2))
else:
  print(0)

Fixed submission:
n = int(input())
A = list(map(int, input().split()))
mod=int(1e9+7)

memo={i:0 for i in range(n)}
for a in A:
  memo[a]=memo.get(a,0)+1

answer=1
if n%2:
  if memo[0]!=1:
    print(0)
    exit()
  for i in range(1, (n+1)//2):
    if memo[2*i]!=2:
      print(0)
      exit()
    else:
      answer = 2*answer %mod
elif not n%2:
  for i in range(n//2):
    if memo[2*i+1]!=2:
      print(0)
      exit()
    else:
      answer = 2*answer %mod
      
print(answer)

Buggy python submission (verdict: Time Limit Exceeded):
N=int(input())
A=list(map(int, input().split()))

if N%2:
  A = A+ [0]

# 0,0,2,2,4,4  5   (i//2)*2 + 1- N%2 0,2,4
# 1,1,3,3,5,5  6

if all([A.count(i)==2 for i in range(1-N%2, N, 2)]):
  print(2**(N//2))
else:
  print(0)

Fixed submission:
n = int(input())
A = list(map(int, input().split()))
mod=int(1e9+7)

memo={i:0 for i in range(n)}
for a in A:
  memo[a]=memo.get(a,0)+1

answer=1
if n%2:
  if memo[0]!=1:
    print(0)
    exit()
  for i in range(1, (n+1)//2):
    if memo[2*i]!=2:
      print(0)
      exit()
    else:
      answer = 2*answer %mod
elif not n%2:
  for i in range(n//2):
    if memo[2*i+1]!=2:
      print(0)
      exit()
    else:
      answer = 2*answer %mod
      
print(answer)