#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
typedef long long int ll;
typedef long double ld;
#define FOR(i,l,r) for(ll i=l;i<r;i++)
#define REP(i,n) FOR(i,0,n)
#define RFOR(i,l,r) for(ll i=r-1;i>=l;i--)
#define RREP(i,n) RFOR(i,0,n)
#define ALL(x) x.begin(),x.end()
#define P pair<ll,ll>
#define F first
#define S second
#define BS(A,x) binary_search(ALL(A),x)
#define LB(A,x) (ll)(lower_bound(ALL(A),x)-A.begin())
#define UB(A,x) (ll)(upper_bound(ALL(A),x)-A.begin())
#define COU(A,x) UB(A,x)-LB(A,x)
template<typename T>using min_priority_queue=priority_queue<T,vector<T>,greater<T>>;
//using mint=modint1000000007;
using mint=modint998244353;
void chmax(ll&a,ll b){a=max(a,b);}
void chmin(ll&a,ll b){a=min(a,b);}
signed main(){
  ll N;cin>>N;
  vector<ll>B(N),K(N);
  REP(i,N)cin>>B[i];
  FOR(i,1,N){
    K[i]=K[i-1];ll s=i;
    while(s%2==0){s/=2;K[i]++;}
  }
  mint zero=1,one=0;
  REP(i,N){
    if(B[i]==1&&K[N-1]==K[i]+K[N-1-i])swap(zero,one);
    if(B[i]==-1){
      if(K[N-1]==K[i]+K[N-1-i])zero+=one,one=zero;
      else zero*=2,one*=2;
    }
  }
  cout<<one.val()<<endl;
  return 0;
}