Buggy python submission (verdict: Runtime Error):
N = int(input())
A = [int(x) for x in input().split()]
mod = 10**9+7
c = 1-N%2
flag = True
di = {}
if(N==1):
    if(A[0]==0):
        print(1)
    else:
        print(0)
else:
    for i in A:
        if(i not in di):
            di[i]=1
        else:
            di[i]+=1
    for i in range(N//2):
        if(i+c==0):
            flag &= (di[i]==1)
        else:
            flag &= (di[i*2+c]==2)
        if(not flag):
            print(0)
            break
    else:
        print((2<<(N//2-1))%mod)


Fixed submission:
N = int(input())
A = [int(x) for x in input().split()]
mod = 10**9+7
c = 1-N%2
flag = True
di = {}
if(N==1):
    if(A[0]==0):
        print(1)
    else:
        print(0)
else:
    for i in A:
        if(i not in di):
            di[i]=1
        else:
            di[i]+=1
    for i in range(N//2):
        if(i+c==0):
            if(0 not in di):
                flag = False
            else:
                flag &= (di[i]==1)
        else:
            if(i*2+c not in di):
                flag = False
            else:
                flag &= (di[i*2+c]==2)
        if(not flag):
            print(0)
            break
    else:
        print((2<<(N//2-1))%mod)

Buggy python submission (verdict: Runtime Error):
N = int(input())
A = [int(x) for x in input().split()]
mod = 10**9+7
c = 1-N%2
flag = True
di = {}
if(N==1):
    if(A[0]==0):
        print(1)
    else:
        print(0)
else:
    for i in A:
        if(i not in di):
            di[i]=1
        else:
            di[i]+=1
    for i in range(N//2):
        if(i+c==0):
            flag &= (di[i]==1)
        else:
            flag &= (di[i*2+c]==2)
        if(not flag):

            else:
                print(0)
            break
    else:
        print((2<<(N//2-1))%mod)


Fixed submission:
N = int(input())
A = [int(x) for x in input().split()]
mod = 10**9+7
c = 1-N%2
flag = True
di = {}
if(N==1):
    if(A[0]==0):
        print(1)
    else:
        print(0)
else:
    for i in A:
        if(i not in di):
            di[i]=1
        else:
            di[i]+=1
    for i in range(N//2):
        if(i+c==0):
            if(0 not in di):
                flag = False
            else:
                flag &= (di[i]==1)
        else:
            if(i*2+c not in di):
                flag = False
            else:
                flag &= (di[i*2+c]==2)
        if(not flag):
            print(0)
            break
    else:
        print((2<<(N//2-1))%mod)

Buggy python submission (verdict: Runtime Error):
N = int(input())
A = [int(x) for x in input().split()]
mod = 10**9+7
c = 1-N%2
flag = True
di = {}
for i in A:
    if(i not in di):
        di[i]=1
    else:
        di[i]+=1
for i in range(N//2):
    if(i+c==0):
        flag &= (di[i]==1)
    else:
        flag &= (di[i*2+c]==2)
    if(not flag):
        if(N==1):
            print(1)
        else:
            print(0)
        break
else:
    print((2<<(N//2-1))%mod)


Fixed submission:
N = int(input())
A = [int(x) for x in input().split()]
mod = 10**9+7
c = 1-N%2
flag = True
di = {}
if(N==1):
    if(A[0]==0):
        print(1)
    else:
        print(0)
else:
    for i in A:
        if(i not in di):
            di[i]=1
        else:
            di[i]+=1
    for i in range(N//2):
        if(i+c==0):
            if(0 not in di):
                flag = False
            else:
                flag &= (di[i]==1)
        else:
            if(i*2+c not in di):
                flag = False
            else:
                flag &= (di[i*2+c]==2)
        if(not flag):
            print(0)
            break
    else:
        print((2<<(N//2-1))%mod)