Buggy python submission (verdict: Time Limit Exceeded):
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time

sys.setrecursionlimit(10**7)
inf=10**20
mod=10**9+7

def LI(): return list(map(int,input().split()))
def I(): return int(input())
def LS(): return input().split()
def S(): return input()

def main():
  n=I()
  l=LI()

  l.sort()

  if n%2==0:
    for i in range(n):
      if (i//2)*2+1!=l[i]:
        return 0
    return pow(2,n//2)%mod

  else:
    if l[0]!=0:
      return 0
    for i in range(n-1):
      if (i//2)*2+2!=l[1:][i]:
        return 0
    return pow(2,n//2)%mod

print(main())


Fixed submission:
a=1000000007
n=int(input())
l=list(map(int,input().split()))
l.sort()
if n%2==1:
  if l[0]!=0:
    print(0)
    exit()
  else:
    l.remove(0)
    sh=2
    f=0
    for i in l:
      if f==0:
        if i!=sh:
          print(0)
          exit()
        else:
          f=1
      else:
        if i!=sh:
          print(0)
          exit()
        else:
          sh+=2
          f=0
  sh=(n-1)//2
  b=1
  for i in range(sh):
    b*=2
    b%=a
  print(b)
else:
  sh=1
  f=0
  for i in l:
    if f==0:
      if i!=sh:
        print(0)
        exit()
      else:
        f=1
    else:
      if i!=sh:
        print(0)
        exit()
      else:
        sh+=2
        f=0
  sh=n//2
  b=1
  for i in range(sh):
    b*=2
    b%=a
  print(b)

Buggy python submission (verdict: Time Limit Exceeded):
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time

sys.setrecursionlimit(10**7)
inf=10**20
mod=10**9+7

def LI(): return list(map(int,input().split()))
def I(): return int(input())
def LS(): return input().split()
def S(): return input()

def main():
  n=I()
  l=LI()

  l.sort()

  x=1
  if n%2==0:
    f=True
    for i in range(n):
      if f:
        f=False
        x*=2
        x%=mod
      else:
        f=True
      if (i//2)*2+1!=l[i]:
        return 0
    return x

  else:
    if l[0]!=0:
      return 0
    f=True
    for i in range(n-1):
      if f:
        f=False
        x*=2
        x%=mod
      else:
        f=True
      if (i//2)*2+2!=l[1:][i]:
        return 0
    return x

print(main())


Fixed submission:
a=1000000007
n=int(input())
l=list(map(int,input().split()))
l.sort()
if n%2==1:
  if l[0]!=0:
    print(0)
    exit()
  else:
    l.remove(0)
    sh=2
    f=0
    for i in l:
      if f==0:
        if i!=sh:
          print(0)
          exit()
        else:
          f=1
      else:
        if i!=sh:
          print(0)
          exit()
        else:
          sh+=2
          f=0
  sh=(n-1)//2
  b=1
  for i in range(sh):
    b*=2
    b%=a
  print(b)
else:
  sh=1
  f=0
  for i in l:
    if f==0:
      if i!=sh:
        print(0)
        exit()
      else:
        f=1
    else:
      if i!=sh:
        print(0)
        exit()
      else:
        sh+=2
        f=0
  sh=n//2
  b=1
  for i in range(sh):
    b*=2
    b%=a
  print(b)

Buggy python submission (verdict: Time Limit Exceeded):
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time

sys.setrecursionlimit(10**7)
inf=10**20
mod=10**9+7

def LI(): return list(map(int,input().split()))
def I(): return int(input())
def LS(): return input().split()
def S(): return input()

def main():
  n=I()
  l=LI()

  l.sort()

  if n%2==0:
    for i in range(n):
      if (i//2)*2+1!=l[i]:
        return 0
    x=1
    for _ in range(n//2):
      x*=2
      x%=mod
    return x

  else:
    if l[0]!=0:
      return 0
    for i in range(n-1):
      if (i//2)*2+2!=l[1:][i]:
        return 0
    x=1
    for _ in range(n//2):
      x*=2
      x%=mod
    return x

print(main())


Fixed submission:
a=1000000007
n=int(input())
l=list(map(int,input().split()))
l.sort()
if n%2==1:
  if l[0]!=0:
    print(0)
    exit()
  else:
    l.remove(0)
    sh=2
    f=0
    for i in l:
      if f==0:
        if i!=sh:
          print(0)
          exit()
        else:
          f=1
      else:
        if i!=sh:
          print(0)
          exit()
        else:
          sh+=2
          f=0
  sh=(n-1)//2
  b=1
  for i in range(sh):
    b*=2
    b%=a
  print(b)
else:
  sh=1
  f=0
  for i in l:
    if f==0:
      if i!=sh:
        print(0)
        exit()
      else:
        f=1
    else:
      if i!=sh:
        print(0)
        exit()
      else:
        sh+=2
        f=0
  sh=n//2
  b=1
  for i in range(sh):
    b*=2
    b%=a
  print(b)

Buggy python submission (verdict: Time Limit Exceeded):
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,random,time

sys.setrecursionlimit(10**7)
inf=10**20
mod=10**9+7

def LI(): return list(map(int,input().split()))
def I(): return int(input())
def LS(): return input().split()
def S(): return input()

def main():
  n=I()
  l=LI()

  l.sort()

  if n%2==0:
    for i in range(n):
      if (i//2)*2+1!=l[i]:
        return 0
    return pow(2,n//2)%mod

  else:
    if l[0]!=0:
      return 0
    for i in range(n-1):
      if (i//2)*2+2!=l[1:][i]:
        return 0
    return pow(2,n//2)%mod

print(main())


Fixed submission:
a=1000000007
n=int(input())
l=list(map(int,input().split()))
l.sort()
if n%2==1:
  if l[0]!=0:
    print(0)
    exit()
  else:
    l.remove(0)
    sh=2
    f=0
    for i in l:
      if f==0:
        if i!=sh:
          print(0)
          exit()
        else:
          f=1
      else:
        if i!=sh:
          print(0)
          exit()
        else:
          sh+=2
          f=0
  sh=(n-1)//2
  b=1
  for i in range(sh):
    b*=2
    b%=a
  print(b)
else:
  sh=1
  f=0
  for i in l:
    if f==0:
      if i!=sh:
        print(0)
        exit()
      else:
        f=1
    else:
      if i!=sh:
        print(0)
        exit()
      else:
        sh+=2
        f=0
  sh=n//2
  b=1
  for i in range(sh):
    b*=2
    b%=a
  print(b)