Buggy python submission (verdict: Time Limit Exceeded):
import sys
imput=sys.stdin.readline
import collections
n=int(input())
a=list(map(int,input().split()))
a.sort()
ans=1
if n%2==1 and collections.Counter(a)[0]==1:
    for i in range(2,n,2):
        if collections.Counter(a)[i]!=2:
            print(0)
            break
        else:
            ans=(ans%(10**9+7))*2%(10**9+7)
    else:
        print(ans%(10**9+7))
elif n%2==0:
    for i in range(1,n,2):
        if collections.Counter(a)[i]!=2:
            print(0)
            break
        else:
            ans=(ans%(10**9+7))*2%(10**9+7)
    else:
        print(ans%(10**9+7))
else:
    print(0)

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

Buggy python submission (verdict: Time Limit Exceeded):
import collections
n=int(input())
a=list(map(int,input().split()))
a.sort()
ans=1
if n%2==1 and collections.Counter(a)[0]==1:
    for i in range(2,n,2):
        if collections.Counter(a)[i]!=2:
            print(0)
            break
        else:
            ans=(ans%(10**9+7))*2%(10**9+7)
    else:
        print(ans%(10**9+7))
elif n%2==0:
    for i in range(1,n,2):
        if collections.Counter(a)[i]!=2:
            print(0)
            break
        else:
            ans=(ans%(10**9+7))*2%(10**9+7)
    else:
        print(ans%(10**9+7))
else:
    print(0)

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

Buggy python submission (verdict: Time Limit Exceeded):
import collections
n=int(input())
a=list(map(int,input().split()))
a.sort()
ans=1
if n%2==1 and collections.Counter(a)[0]==1:
    for i in range(2,n,2):
        if collections.Counter(a)[i]!=2:
            print(0)
            break
        else:
            ans=ans*2%(10**9+7)
    else:
        print(ans%(10**9+7))
elif n%2==0:
    for i in range(1,n,2):
        if collections.Counter(a)[i]!=2:
            print(0)
            break
        else:
            ans=ans*2%(10**9+7)
    else:
        print(ans%(10**9+7))
else:
    print(0)

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

Buggy python submission (verdict: Time Limit Exceeded):
import collections
n=int(input())
a=list(map(int,input().split()))
a.sort()

if n%2==1 and collections.Counter(a)[0]==1:
    for i in range(2,n,2):
        if collections.Counter(a)[i]!=2:
            print(0)
            break
    else:
        print(2**(n//2)%(10**9+7))
elif n%2==0:
    for i in range(1,n,2):
        if collections.Counter(a)[i]!=2:
            print(0)
            break
    else:
        print(2**(n//2)%(10**9+7))
else:
    print(0)

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