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

ans = 1
count = 0
if N == 1:
    if A[0] == 0:
        ans = 1
    else:
        print(0)

if N % 2 == 0:
    for i in range(1, int(N/2)+1):
        if A[i*2-1] == 2:
            count += 1
        else:
            ans = 0
else:
    if A.count(0) == 1:
        for i in range(1, int(N/2)+1):
            if A[i*2] == 2:
                count += 1

            else:
                ans = 0
    else:
        ans = 0
for i in range(count):
    ans *= 2
    ans %= 1000000007
print(ans)


Fixed submission:
import collections
N = int(input())
A = list(map(int,input().split()))
A.sort()
A = collections.Counter(A)

ans = 1
count = 0
if N == 1:
    if A[0] == 1:
        ans = 1
    else:
        ans = 0

elif N % 2 == 0:
    for i in range(1, int(N/2)+1):
        if A[i*2-1] == 2:
            count += 1
        else:
            ans = 0
else:
    if A[0] == 1:
        for i in range(1, int(N/2)+1):
            if A[i*2] == 2:
                count += 1

            else:
                ans = 0
    else:
        ans = 0
for i in range(count):
    ans *= 2
    ans %= 1000000007
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
import collections
N = int(input())
A = list(map(int,input().split()))
ans = 1
count = 0
if N == 1:
    if A[0] == 0:
        ans = 1
    else:
        print(0)

if N % 2 == 0:
    for i in range(1, int(N/2)+1):
        if A.count(i*2-1) == 2:
            count += 1
        else:
            ans = 0
else:
    if A.count(0) == 1:
        for i in range(1, int(N/2)+1):
            if A.count(i*2) == 2:
                count += 1

            else:
                ans = 0
    else:
        ans = 0
for i in range(count):
    ans *= 2
    ans %= 1000000007
print(ans)


Fixed submission:
import collections
N = int(input())
A = list(map(int,input().split()))
A.sort()
A = collections.Counter(A)

ans = 1
count = 0
if N == 1:
    if A[0] == 1:
        ans = 1
    else:
        ans = 0

elif N % 2 == 0:
    for i in range(1, int(N/2)+1):
        if A[i*2-1] == 2:
            count += 1
        else:
            ans = 0
else:
    if A[0] == 1:
        for i in range(1, int(N/2)+1):
            if A[i*2] == 2:
                count += 1

            else:
                ans = 0
    else:
        ans = 0
for i in range(count):
    ans *= 2
    ans %= 1000000007
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
import collections
N = int(input())
A = list(map(int,input().split()))
ans = 1
count = 0
if N == 1:
    if A[0] == 0:
        ans = 1
    else:
        print(0)

if N % 2 == 0:
    for i in range(1, int(N/2)+1):
        if A.count(i*2-1) == 2:
            count += 1
        else:
            ans = 0
else:
    if A.count(0) == 1:
        for i in range(1, int(N/2)+1):
            if A.count(i*2) == 2:
                count += 1

            else:
                ans = 0
    else:
        ans = 0
for i in range(count):
    ans *= 2
    ans %= 1000000007
print(ans)


Fixed submission:
import collections
N = int(input())
A = list(map(int,input().split()))
A.sort()
A = collections.Counter(A)

ans = 1
count = 0
if N == 1:
    if A[0] == 1:
        ans = 1
    else:
        ans = 0

elif N % 2 == 0:
    for i in range(1, int(N/2)+1):
        if A[i*2-1] == 2:
            count += 1
        else:
            ans = 0
else:
    if A[0] == 1:
        for i in range(1, int(N/2)+1):
            if A[i*2] == 2:
                count += 1

            else:
                ans = 0
    else:
        ans = 0
for i in range(count):
    ans *= 2
    ans %= 1000000007
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
import collections
N = int(input())
A = list(map(int,input().split()))
ans = 1
if N == 1:
    if A[0] == 0:
        ans = 1
    else:
        print(0)

if N % 2 == 0:
    for i in range(1, int(N/2)+1):
        if A.count(i*2-1) == 2:
            ans *= 2
            ans %= 1000000007
        else:
            ans *= 0
else:
    if A.count(0) == 1:
        for i in range(1, int(N/2)+1):
            if A.count(i*2) == 2:
                ans *= 2
                ans %= 1000000007
            else:
                ans *=0
    else:
        ans *= 0
print(ans)


Fixed submission:
import collections
N = int(input())
A = list(map(int,input().split()))
A.sort()
A = collections.Counter(A)

ans = 1
count = 0
if N == 1:
    if A[0] == 1:
        ans = 1
    else:
        ans = 0

elif N % 2 == 0:
    for i in range(1, int(N/2)+1):
        if A[i*2-1] == 2:
            count += 1
        else:
            ans = 0
else:
    if A[0] == 1:
        for i in range(1, int(N/2)+1):
            if A[i*2] == 2:
                count += 1

            else:
                ans = 0
    else:
        ans = 0
for i in range(count):
    ans *= 2
    ans %= 1000000007
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
import collections
N = int(input())
A = list(map(int,input().split()))
ans = 1
if N == 1:
    if A[0] == 0:
        ans = 1
    else:
        print(0)

if N % 2 == 0:
    for i in range(1, int(N/2)+1):
        if A.count(i*2-1) == 2:
            ans *= 2
            ans %= 1000000007
        else:
            ans *= 0
else:
    if A.count(0) == 1:
        for i in range(1, int(N/2)+1):
            if A.count(i*2) == 2:
                ans *= 2
                ans %= 1000000007
            else:
                ans *=0
    else:
        ans *= 0
print(ans)


Fixed submission:
import collections
N = int(input())
A = list(map(int,input().split()))
A.sort()
A = collections.Counter(A)

ans = 1
count = 0
if N == 1:
    if A[0] == 1:
        ans = 1
    else:
        ans = 0

elif N % 2 == 0:
    for i in range(1, int(N/2)+1):
        if A[i*2-1] == 2:
            count += 1
        else:
            ans = 0
else:
    if A[0] == 1:
        for i in range(1, int(N/2)+1):
            if A[i*2] == 2:
                count += 1

            else:
                ans = 0
    else:
        ans = 0
for i in range(count):
    ans *= 2
    ans %= 1000000007
print(ans)