Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
A = list(map(int,input().split()))
d = N // 2
a = [i for i in set(A) if A.count(i) == 2 and i != 0]
# ans = []
# def linking_up():
# ans_1 = [ i for i in range(N) if i % 2 == 1 and i!= 0 and A.count(i) == 2]
    # for i in range(N):
        # if i % 2 == 0 and i != 0:
            # if A.count(i) == 2 and A.count(0) == 1:
                # ans.append('c')
# ans_2 = [ i for i in range(N) if i % 2 == 0 and A.count(i) == 2]
        # else:
            # if A.count(i) == 2:
                # ans.append('a')
# linking_up()
if len(a) == d:
    a = (2 ** d) % (10 ** 9 + 7)
    print(a)
else:
    print(0)
        




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

Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
A = list(map(int,input().split()))
d = N // 2
ans = []
def linking_up():
    for i in range(N):
        if i % 2 == 0 and i != 0:
            if A.count(i) == 2 and A.count(0) == 1:
                ans.append('c')
        else:
            if A.count(i) == 2:
                ans.append('a')
linking_up()
if ans.count('a') == d or ans.count('c')== d:
    a = (2 ** d) % (10 ** 9 + 7)
    print(a)
else:
    print(0)
        




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

Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
A = list(map(int,input().split()))
d = N // 2
# ans = []
# def linking_up():
ans_1 = [ i for i in range(N) if i % 2 == 0 and i != 0 and A.count(i) == 2 and A.count(0) == 1]
    # for i in range(N):
        # if i % 2 == 0 and i != 0:
            # if A.count(i) == 2 and A.count(0) == 1:
                # ans.append('c')
ans_2 = [ i for i in range(N) if i % 2 and A.count(i) == 2]
        # else:
            # if A.count(i) == 2:
                # ans.append('a')
# linking_up()
if len(ans_1) == d or len(ans_2) == d:
    print(2 ** d)
else:
    print(0)
        




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

Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
A = list(map(int,input().split()))
d = N // 2
ans = []
def linking_up():
    for i in range(N):
        if i % 2 == 0 and i != 0:
            if A.count(i) == 2 and A.count(0) == 1:
                ans.append('c')
        else:
            if A.count(i) == 2:
                ans.append('a')
linking_up()
if ans.count('a') == d or ans.count('c')== d:
    print(2 ** d)
else:
    print(0)
        




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

Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
A = list(map(int,input().split()))
d = N // 2
ans = []
def linking_up():
    for i in range(N):
        if i % 2 == 0 and i != 0:
            if A.count(i) == 2 and A.count(0) == 1:
                ans.append('c')
            else:
                ans.append('b')
        else:
            if A.count(i) == 2:
                ans.append('a')
            else:
                ans.append('b')
linking_up()
if ans.count('a') == d or ans.count('c')== d:
    print(2 ** d)
else:
    print(0)
        




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

Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
A = list(map(int,input().split()))
d = N // 2
ans = []
def linking_up():
    for i in range(N):
        if i % 2 == 1:
            if A.count(i) == 2:
                ans.append('a')
            else:
                ans.append('b')
        elif i % 2 == 0 and i != 0:
            if A.count(i) == 2 and A.count(0) == 1:
                ans.append('c')
            else:
                ans.append('b')
linking_up()
if ans.count('a') == d or ans.count('c')== d:
    print(2 ** d)
else:
    print(0)
        




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

Buggy python submission (verdict: Time Limit Exceeded):
N = int(input())
A = list(map(int,input().split()))
d = N // 2
ans = []
def linking_up():
    if N % 2 == 0:
        for i in range(N):
            if i % 2 == 1:
                if A.count(i) == 2:
                    ans.append('a')
                else:
                    ans.append('b')
    else:
        for i in range(N):
            if i % 2 == 0 and i != 0:
                if A.count(i) == 2 and A.count(0) == 1:
                    ans.append('a')
                else:
                    ans.append('b')
linking_up()
if ans.count('a') == d:
    print(2 ** d)
else:
    print(0)
        




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