def lucas(n,k):
  while max(n,k):
    if n&1==0 and k&1==1:
      return 0
    n>>=1
    k>>=1
  return 1

N=int(input())
B=list(map(int,input().split()))
DP=[[0,0] for i in range(N+1)]
DP[0][0]=1
mod=998244353
for i in range(N):
  for j in range(2):
    for k in range(2):
      if B[i]==k or B[i]==-1:
        x=lucas(N-1,i)
        DP[i+1][j^(k*x)]=(DP[i+1][j^(k*x)]+DP[i][j])%mod
print(DP[N][1])