#include<iostream>
#include<string>
#include<cstdio>
#include<vector>
#include<cmath>
#include<algorithm>
#include<functional>
#include<iomanip>
#include<queue>
#include<ciso646>
#include<random>
#include<map>
#include<set>
#include<complex>
#include<bitset>
#include<stack>
#include<unordered_map>
#include<utility>
#include<tuple>
#include<cassert>
using namespace std;
typedef long long ll;
typedef unsigned int ui;
const ll mod = 998244353;
const ll INF = (ll)1000000007 * 1000000007;
typedef pair<int, int> P;
#define stop char nyaa;cin>>nyaa;
#define rep(i,n) for(int i=0;i<n;i++)
#define per(i,n) for(int i=n-1;i>=0;i--)
#define Rep(i,sta,n) for(int i=sta;i<n;i++)
#define Per(i,sta,n) for(int i=n-1;i>=sta;i--)
#define rep1(i,n) for(int i=1;i<=n;i++)
#define per1(i,n) for(int i=n;i>=1;i--)
#define Rep1(i,sta,n) for(int i=sta;i<=n;i++)
typedef long double ld;
const ld eps = 1e-8;
const ld pi = acos(-1.0);
typedef pair<ll, ll> LP;
int dx[4]={1,-1,0,0};
int dy[4]={0,0,1,-1};
template<class T>bool chmax(T &a, const T &b) {if(a<b){a=b;return 1;}return 0;}
template<class T>bool chmin(T &a, const T &b) {if(b<a){a=b;return 1;}return 0;}

template<int mod>
struct ModInt {
    long long x;
 
    ModInt() : x(0) {}
    ModInt(long long y) : x(y >= 0 ? y % mod : (mod - (-y) % mod) % mod) {}

    explicit operator int() const {return x;}
 
    ModInt &operator+=(const ModInt &p) {
        if((x += p.x) >= mod) x -= mod;
        return *this;
    }
    ModInt &operator-=(const ModInt &p) {
        if((x += mod - p.x) >= mod) x -= mod;
        return *this;
    }
    ModInt &operator*=(const ModInt &p) {
        x = (int)(1LL * x * p.x % mod);
        return *this;
    }
    ModInt &operator/=(const ModInt &p) {
        *this *= p.inverse();
        return *this;
    }
 
    ModInt operator-() const { return ModInt(-x); }
    ModInt operator+(const ModInt &p) const { return ModInt(*this) += p; }
    ModInt operator-(const ModInt &p) const { return ModInt(*this) -= p; }
    ModInt operator*(const ModInt &p) const { return ModInt(*this) *= p; }
    ModInt operator/(const ModInt &p) const { return ModInt(*this) /= p; }
 
    bool operator==(const ModInt &p) const { return x == p.x; }
    bool operator!=(const ModInt &p) const { return x != p.x; }
 
    ModInt inverse() const{
        int a = x, b = mod, u = 1, v = 0, t;
        while(b > 0) {
            t = a / b;
            a -= t * b;
            swap(a, b);
            u -= t * v;
            swap(u, v);
        }
        return ModInt(u);
    }

    ModInt power(long long p) const{
        int a = x;
        if (p==0) return 1;
        if (p==1) return ModInt(a);
        if (p%2==1) return (ModInt(a)*ModInt(a)).power(p/2)*ModInt(a);
        else return (ModInt(a)*ModInt(a)).power(p/2);
    }

    ModInt power(const ModInt p) const{
        return ((ModInt)x).power(p.x);
    }

    friend ostream &operator<<(ostream &os, const ModInt<mod> &p) {
        return os << p.x;
    }
    friend istream &operator>>(istream &is, ModInt<mod> &a) {
        long long x;
        is >> x;
        a = ModInt<mod>(x);
        return (is);
    }
};

using modint = ModInt<mod>;



int n;
int a[200010];
int negnum[200010];
int nxt2[200010][2],nxt0[200010];
vector<int> v;
modint dp[200010][2];
modint pow2[200010];

void solve(){
    cin >> n;
    pow2[0]=1;
    rep(i,n) pow2[i+1]=pow2[i]*2;
    rep(i,n) cin >> a[i];
    rep(i,n) negnum[i+1]=negnum[i]+(a[i]<0);
    rep(i,n){
        dp[i+1][negnum[i+1]%2]=dp[i][negnum[i+1]%2]+pow2[max(0,n-i-2)];
        dp[i+1][1-negnum[i+1]%2]=dp[i][1-negnum[i+1]%2];
    }
    nxt2[n][0]=n;nxt2[n][1]=n;nxt0[n]=n;
    per(i,n){
        nxt2[i][0]=nxt2[i+1][0];
        nxt2[i][1]=nxt2[i+1][1];
        nxt0[i]=nxt0[i+1];
        if(abs(a[i])==2){
            nxt2[i][1]=nxt2[i][0];
            nxt2[i][0]=i;
        }
        if(a[i]==0){
            nxt0[i]=i;
        }
    }
    modint ans=0;
    rep(i,n){
        if(nxt2[i][0]>nxt0[i]) continue;
        int r=min(nxt2[i][1],nxt0[i]);
        //cout << i << " " << nxt2[i][0] << " " << r << endl;
        int z=negnum[i];z%=2;
        //cout << z << endl;
        //cout << pow2[max(0,i-1)]*(dp[r][1-z]-dp[nxt2[i][0]][1-z]) << endl;
        ans+=pow2[max(0,i-1)]*(dp[r][1-z]-dp[nxt2[i][0]][1-z]);
    }
    cout << ans/pow2[n-1] << endl;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << fixed << setprecision(50);
    solve();
}