#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <queue>
#include <string>
#include <map>
#include <set>
#include <stack>
#include <tuple>
#include <deque>
#include <array>
#include <numeric>
#include <bitset>
#include <iomanip>
#include <cassert>
#include <chrono>
#include <random>
#include <limits>
#include <iterator>
#include <functional>
#include <sstream>
#include <fstream>
#include <complex>
#include <cstring>
#include <unordered_map>
#include <unordered_set>
using namespace std;

using ll = long long;
using P = pair<int, int>;
constexpr int INF = 1001001001;
// constexpr int mod = 1000000007;
constexpr int mod = 998244353;

template<class T>
inline bool chmax(T& x, T y){
    if(x < y){
        x = y;
        return true;
    }
    return false;
}
template<class T>
inline bool chmin(T& x, T y){
    if(x > y){
        x = y;
        return true;
    }
    return false;
}

struct mint {
    int x;
    mint() : x(0) {}
    mint(int64_t y) : x(y >= 0 ? y % mod : (mod - (-y) % mod) % mod) {}
    mint& operator+=(const mint& p){
        if((x += p.x) >= mod)   x -= mod;
        return *this;
    }
    mint& operator-=(const mint& p){
        if((x -= p.x) < 0)  x += mod;
        return *this;
    }
    mint& operator*=(const mint& p){
        x = (int)(1LL * x * p.x % mod);
        return *this;
    }
    mint& operator/=(const mint& p){
        *this *= p.inverse();
        return *this;
    }
    mint operator-() const { return mint(-x); }
    mint operator+(const mint& p) const { return mint(*this) += p; }
    mint operator-(const mint& p) const { return mint(*this) -= p; }
    mint operator*(const mint& p) const { return mint(*this) *= p; }
    mint operator/(const mint& p) const { return mint(*this) /= p; }
    bool operator==(const mint& p) const { return x == p.x; }
    bool operator!=(const mint& p) const { return x != p.x; }
    mint pow(int64_t n) const {
        mint res = 1, mul = x;
        while(n > 0){
            if(n & 1)   res *= mul;
            mul *= mul;
            n >>= 1;
        }
        return res;
    }
    mint inverse() const { return pow(mod - 2); }
    friend ostream& operator<<(ostream& os, const mint& p){
        return os << p.x;
    }
    friend istream& operator>>(istream& is, mint& p){
        int64_t val;
        is >> val;
        p = mint(val);
        return is;
    }
};

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int n;
    cin >> n;
    vector<int> a(n);
    for(int i = 0; i < n; ++i)  cin >> a[i];

    vector<mint> pow2(n + 1, 1);
    for(int i = 0; i < n; ++i)  pow2[i + 1] = pow2[i] * 2;
    
    mint ans = 0;
    for(int i = 0; i < n; ++i){
        if(abs(a[i]) < 2)   continue;
        mint plus = pow2[max(0, i - 1)], minus = 0;
        int prod = 1;
        for(int j = i - 1; j >= 0; --j){
            if(abs(a[j]) != 1)  break;
            prod *= a[j];
            if(prod > 0)    plus += pow2[max(0, j - 1)];
            else    minus += pow2[max(0, j - 1)];
        }
        ans += pow2[max(0, n - i - 2)] * (a[i] > 0 ? minus : plus);
        prod = a[i];
        for(int j = i + 1; j < n; ++j){
            if(abs(a[j]) != 1)  break;
            prod *= a[j];
            if(prod > 0)    ans += pow2[max(0, n - j - 2)] * minus;
            else    ans += pow2[max(0, n - j - 2)] * plus;
        }
    }

    cout << ans / pow2[n - 1] << endl;

    return 0;
}