#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
#define _GLIBCXX_DEBUG
using namespace std;
using std::cout;
using std::cin;
using std::endl;
using ll=long long;
using ld=long double;
ll ILL=1167167167167167167;
const int INF=2100000000;
const ll mod=998244353;
#define rep(i,a) for (int i=0;i<a;i++)
#define all(p) p.begin(),p.end()
template<class T> using _pq = priority_queue<T, vector<T>, greater<T>>;
template<class T> ll LB(vector<T> &v,T a){return lower_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> ll UB(vector<T> &v,T a){return upper_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> bool chmin(T &a,const T &b){if(a>b){a=b;return 1;}else return 0;}
template<class T> bool chmax(T &a,const T &b){if(a<b){a=b;return 1;}else return 0;}
template<class T> void So(vector<T> &v) {sort(v.begin(),v.end());}
template<class T> void Sore(vector<T> &v) {sort(v.begin(),v.end(),[](T x,T y){return x>y;});}
void yneos(bool a){if(a) cout<<"Yes\n"; else cout<<"No\n";}
template<class T> void vec_out(vector<T> &p){for(int i=0;i<(int)(p.size());i++){if(i) cout<<" ";cout<<p[i];}cout<<"\n";}



void solve();
// oddloop
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	
	int t=1;
	//cin>>t;
	rep(i,t) solve();
}

void solve(){
	int N;
	cin>>N;
	vector<int> A(N);
	rep(i,N) cin>>A[i];
	vector<ll> p(N+1),rev(N+1);
	p[0]=1;
	rev[0]=1;
	rep(i,N) p[i+1]=(p[i]*2ll)%mod,rev[i+1]=(rev[i]*((mod+1)/2))%mod;
	ll ans=0;
	int tmp=1;
	rep(i,N){
		tmp*=A[i];
		if(abs(tmp)>2) break;
		if(tmp==-2) ans=(ans+rev[i+1])%mod;
	}
	tmp=1;
	for(int i=N-1;i>=0;i--){
		tmp*=A[i];
		if(abs(tmp)>2) break;
		if(tmp==-2) ans=(ans+rev[N-i])%mod;
	}
	int l=0;
	A[0]=1;
	tmp=1;
	for(int r=1;r<N;r++){
		if(A[r]==0||r==N-1){
			int len=0;
			int x=0;
			vector<vector<ll>> ch={{0,0}},mo={{0,0}};
			for(int i=l;i<r;i++){
				if(abs(A[i])==2) len++,ch.push_back({0,0}),mo.push_back({0,0});
				if(A[i]<0) x^=1;
				ch[len][x]=(ch[len][x]+p[i])%mod;
				mo[len][x]=(mo[len][x]+rev[i+1])%mod;
			}
			rep(i,len){
				ans=(ans+(ch[i][0]*mo[i+1][1])%mod)%mod;
				ans=(ans+(ch[i][1]*mo[i+1][0])%mod)%mod;
			}
			l=r;
			A[r]=1;
		}
	}
	cout<<ans<<"\n";
}