#include<bits/stdc++.h>
using namespace std;
#define rep(i,n) for(ll i=0;i<n;i++)
#define repl(i,l,r) for(ll i=(l);i<(r);i++)
#define per(i,n) for(ll i=n-1;i>=0;i--)
#define perl(i,r,l) for(ll i=r-1;i>=l;i--)
#define fi first
#define se second
#define pb push_back
#define ins insert
#define pqueue(x) priority_queue<x,vector<x>,greater<x>>
#define all(x) (x).begin(),(x).end()
#define CST(x) cout<<fixed<<setprecision(x)
#define rev(x) reverse(x);
using ll=long long;
using vl=vector<ll>;
using vvl=vector<vector<ll>>;
using pl=pair<ll,ll>;
using vpl=vector<pl>;
using vvpl=vector<vpl>;
const ll MOD=1000000007;
const ll MOD9=998244353;
const int inf=1e9+10;
const ll INF=4e18;
const ll dy[8]={1,0,-1,0,1,1,-1,-1};
const ll dx[8]={0,-1,0,1,1,-1,1,-1};
template<class T> inline bool chmin(T& a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template<class T> inline bool chmax(T& a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

const int mod = MOD9;
const int max_n = 200005;
struct mint {
  ll x; // typedef long long ll;
  mint(ll x=0):x((x%mod+mod)%mod){}
  mint operator-() const { return mint(-x);}
  mint& operator+=(const mint a) {
    if ((x += a.x) >= mod) x -= mod;
    return *this;
  }
  mint& operator-=(const mint a) {
    if ((x += mod-a.x) >= mod) x -= mod;
    return *this;
  }
  mint& operator*=(const mint a) { (x *= a.x) %= mod; return *this;}
  mint operator+(const mint a) const { return mint(*this) += a;}
  mint operator-(const mint a) const { return mint(*this) -= a;}
  mint operator*(const mint a) const { return mint(*this) *= a;}
  mint pow(ll t) const {
    if (!t) return 1;
    mint a = pow(t>>1);
    a *= a;
    if (t&1) a *= *this;
    return a;
  }
  bool operator==(const mint &p) const { return x == p.x; }
  bool operator!=(const mint &p) const { return x != p.x; }
  // for prime mod
  mint inv() const { return pow(mod-2);}
  mint& operator/=(const mint a) { return *this *= a.inv();}
  mint operator/(const mint a) const { return mint(*this) /= a;}
};
istream& operator>>(istream& is, mint& a) { return is >> a.x;}
ostream& operator<<(ostream& os, const mint& a) { return os << a.x;}

int main(){
    mint ans=0;
    ll n;cin >> n;
    vl a(n);rep(i,n)cin >> a[i];
    rep(i,n){
        if(abs(a[i])!=2)continue;
        vl lp,lm,rp,rm;
        ll cnt=1;
        per(j,i){
            if(abs(a[j])!=1)break;
            cnt*=a[j];
            if(cnt==1)lp.push_back(j);
            else lm.push_back(j);
        }
        cnt=1;
        repl(j,i+1,n){
            if(abs(a[j])!=1)break;
            cnt*=a[j];
            if(cnt==1)rp.push_back(j);
            else rm.push_back(j);
        }
        if(a[i]==-2){
            //lm.push_back(i);rm.push_back(i);
            lp.push_back(i);rp.push_back(i);
            mint ra=0,rb=0,rc=0,rd=0;
            for(auto z:lp){
                ra+=mint(2).pow(max(0LL,z-1));
            }
            for(auto z:rp){
                rb+=mint(2).pow(max(0LL,n-z-2));
            }
            for(auto z:lm){
                rc+=mint(2).pow(max(0LL,z-1));
            }
            for(auto z:rm){
                rd+=mint(2).pow(max(0LL,n-z-2));
            }
            ans+=ra*rb+rc*rd;//-mint(2).pow(n-2);
            //cout << ans <<endl;
        }
        else{
            lp.push_back(i);rp.push_back(i);
            mint ra=0,rb=0,rc=0,rd=0;
            for(auto z:lp){
                ra+=mint(2).pow(max(0LL,z-1));
            }
            for(auto z:rp){
                rb+=mint(2).pow(max(0LL,n-z-2));
            }
            for(auto z:lm){
                rc+=mint(2).pow(max(0LL,z-1));
            }
            for(auto z:rm){
                rd+=mint(2).pow(max(0LL,n-z-2));
            }
            ans+=ra*rd+rc*rb;//-mint(2).pow(n-2);
            //cout << ans <<endl;
        }
    }
    cout << ans/mint(2).pow(n-1) <<endl;
}