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

A.sort()
i = 0
res = 0
if N % 2 == 1:
  res = 1
  i = 1
  if A[0] == A[1]:
    print(0)
    exit(0)
  if A[0] == 1:
    print(0)
    exit(0)
else:
  res = 2
  i = 2
  if A[0] != A[1]:
    print(0)
    exit(0)
  if A[0] == 0:
    print(0)
    exit(0)
while i < N - 1:
  if A[i] == A[i + 1]:
    if N % 2 == 0:
      if A[i] != 2 * (i / 2 + 1) - 1:
        res = 0
        break
    else:
      if A[i] != 2 * (i // 2 + 1):
        res = 0
        break
    res *= 2
    i += 2
  else:
    res = 0
    break
print(res)



Fixed submission:
N = int(input())
A = list(map(int, input().split()))

A.sort()
mod = 10 ** 9 + 7
i = 0
res = 0
if N == 1:
  if A[0] == 0:
    print(1)
  else:
    print(0)
  exit(0)
if N % 2 == 1:
  res = 1
  i = 1
  if A[0] == A[1]:
    print(0)
    exit(0)
  if A[0] == 1:
    print(0)
    exit(0)
else:
  res = 2
  i = 2
  if A[0] != A[1]:
    print(0)
    exit(0)
  if A[0] == 0:
    print(0)
    exit(0)
while i < N - 1:
  if A[i] == A[i + 1]:
    if N % 2 == 0:
      if A[i] != 2 * (i / 2 + 1) - 1:
        res = 0
        break
    else:
      if A[i] != 2 * (i // 2 + 1):
        res = 0
        break
    res *= 2
    i += 2
  else:
    res = 0
    break
print(res % mod)

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

A.sort()
i = 0
if N % 2 == 1:
  i = 1
  if A[0] == A[1]:
    print(0)
    exit(0)
  if A[0] == 1:
    print(0)
    exit(0)
else:
  i = 2
  if A[0] != A[1]:
    print(0)
    exit(0)
  if A[0] == 0:
    print(0)
    exit(0)
res = 1
while i < N - 1:
  if A[i] == A[i + 1]:
    if N % 2 == 0:
      if A[i] != 2 * (i / 2 + 1) - 1:
        res = 0
        break
    else:
      if A[i] != 2 * (i // 2 + 1):
        res = 0
        break
    res *= 2
    i += 2
  else:
    res = 0
    break
print(res)

Fixed submission:
N = int(input())
A = list(map(int, input().split()))

A.sort()
mod = 10 ** 9 + 7
i = 0
res = 0
if N == 1:
  if A[0] == 0:
    print(1)
  else:
    print(0)
  exit(0)
if N % 2 == 1:
  res = 1
  i = 1
  if A[0] == A[1]:
    print(0)
    exit(0)
  if A[0] == 1:
    print(0)
    exit(0)
else:
  res = 2
  i = 2
  if A[0] != A[1]:
    print(0)
    exit(0)
  if A[0] == 0:
    print(0)
    exit(0)
while i < N - 1:
  if A[i] == A[i + 1]:
    if N % 2 == 0:
      if A[i] != 2 * (i / 2 + 1) - 1:
        res = 0
        break
    else:
      if A[i] != 2 * (i // 2 + 1):
        res = 0
        break
    res *= 2
    i += 2
  else:
    res = 0
    break
print(res % mod)

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

A.sort()
i = 0
if N % 2 == 1:
  i = 1
  if A[0] == A[1]:
    print(0)
    exit(0)
  if A[0] == 1:
    print(0)
    exit(0)
else:
  i = 2
  if A[0] != A[1]:
    print(0)
    exit(0)
  if A[0] == 0:
    print(0)
    exit(0)
res = 1
while i < N - 1:
  print("a", i)
  if A[i] == A[i + 1]:
    if N % 2 == 0:
      if A[i] != 2 * (i / 2 + 1) - 1:
        res = 0
        break
    else:
      if A[i] != 2 * (i // 2 + 1):
        res = 0
        break
    res *= 2
    i += 2
  else:
    res = 0
    break
print(res)



Fixed submission:
N = int(input())
A = list(map(int, input().split()))

A.sort()
mod = 10 ** 9 + 7
i = 0
res = 0
if N == 1:
  if A[0] == 0:
    print(1)
  else:
    print(0)
  exit(0)
if N % 2 == 1:
  res = 1
  i = 1
  if A[0] == A[1]:
    print(0)
    exit(0)
  if A[0] == 1:
    print(0)
    exit(0)
else:
  res = 2
  i = 2
  if A[0] != A[1]:
    print(0)
    exit(0)
  if A[0] == 0:
    print(0)
    exit(0)
while i < N - 1:
  if A[i] == A[i + 1]:
    if N % 2 == 0:
      if A[i] != 2 * (i / 2 + 1) - 1:
        res = 0
        break
    else:
      if A[i] != 2 * (i // 2 + 1):
        res = 0
        break
    res *= 2
    i += 2
  else:
    res = 0
    break
print(res % mod)

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

A.sort(reverse = True)
if N % 2 == 1:
  if A.count(A[-1]) == 0:
    print(0)
    exit(0)
else:
  if A.count(A[-1]) == 1:
    print(0)
    exit(0)
res = 1
i = 0
while i <= N - 1:
  if A[i] == A[i + 1]:
    res *= 2
    i += 2
  else:
    res = 0
    break
print(res)



Fixed submission:
N = int(input())
A = list(map(int, input().split()))

A.sort()
mod = 10 ** 9 + 7
i = 0
res = 0
if N == 1:
  if A[0] == 0:
    print(1)
  else:
    print(0)
  exit(0)
if N % 2 == 1:
  res = 1
  i = 1
  if A[0] == A[1]:
    print(0)
    exit(0)
  if A[0] == 1:
    print(0)
    exit(0)
else:
  res = 2
  i = 2
  if A[0] != A[1]:
    print(0)
    exit(0)
  if A[0] == 0:
    print(0)
    exit(0)
while i < N - 1:
  if A[i] == A[i + 1]:
    if N % 2 == 0:
      if A[i] != 2 * (i / 2 + 1) - 1:
        res = 0
        break
    else:
      if A[i] != 2 * (i // 2 + 1):
        res = 0
        break
    res *= 2
    i += 2
  else:
    res = 0
    break
print(res % mod)

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

A.sort(reverse = True)
if N % 2 == 1:
  if A.count(A[-1]) == 0:
    print(0)
    exit(0)
else:
  if A.count(A[-1]) == 1:
    print(0)
    exit(0)
res = 1
temp = 0
for i in range(N):
  if A.count(A[i]) == 2:
    if temp == A[i]:
      continue
    res *= 2
  else:
    if i == N - 1:
      continue
    res = 0
    break
  temp = A[i]
print(res)

Fixed submission:
N = int(input())
A = list(map(int, input().split()))

A.sort()
mod = 10 ** 9 + 7
i = 0
res = 0
if N == 1:
  if A[0] == 0:
    print(1)
  else:
    print(0)
  exit(0)
if N % 2 == 1:
  res = 1
  i = 1
  if A[0] == A[1]:
    print(0)
    exit(0)
  if A[0] == 1:
    print(0)
    exit(0)
else:
  res = 2
  i = 2
  if A[0] != A[1]:
    print(0)
    exit(0)
  if A[0] == 0:
    print(0)
    exit(0)
while i < N - 1:
  if A[i] == A[i + 1]:
    if N % 2 == 0:
      if A[i] != 2 * (i / 2 + 1) - 1:
        res = 0
        break
    else:
      if A[i] != 2 * (i // 2 + 1):
        res = 0
        break
    res *= 2
    i += 2
  else:
    res = 0
    break
print(res % mod)