def base10int(n,base):
  x=[]
  while n!=0:
    x.append(n%base)
    n//=base
  return x[::-1]

def comb(n,r):
  if r>n:
    return 0
  tmp1=1
  tmp2=1
  for i in range(r):
    tmp1*=n-i
    tmp2*=i+1
  return tmp1//tmp2

def lucas(n,k,p):
  # nCk mod p を求める
  np=base10int(n,p)
  kp=base10int(k,p)
  kp=[0]*(len(np)-len(kp))+kp
  tmp=1
  for ni,ki in zip(np,kp):
    tmp*=comb(ni,ki)
    tmp%=p
  return tmp

n=int(input())
b=list(map(int,input().split()))
mod=998244353
dp=[1,0]
for i in range(n):
  m=lucas(n-1,i,2)
  if b[i]==0:
    pass
  if b[i]==1:
    if m==1:
      dp=[dp[1],dp[0]]
  if b[i]==-1:
    if m==0:
      dp=[2*dp[0]%mod,2*dp[1]%mod]
    else:
      dp=[(dp[0]+dp[1])%mod]*2
print(dp[1])