#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>
#include <climits>
#include <cstring>
#include <cassert>


using namespace std;
//using namespace atcoder;

#define REP(i, n) for (int i=0; i<(n); ++i)
#define RREP(i, n) for (int i=(int)(n)-1; i>=0; --i)
#define FOR(i, a, n) for (int i=(a); i<(n); ++i)
#define RFOR(i, a, n) for (int i=(int)(n)-1; i>=(a); --i)

#define SZ(x) ((int)(x).size())
#define ALL(x) (x).begin(),(x).end()

#define DUMP(x) cerr<<#x<<" = "<<(x)<<endl
#define DEBUG(x) cerr<<#x<<" = "<<(x)<<" (L"<<__LINE__<<")"<<endl;

template<class T>
ostream &operator<<(ostream &os, const vector<T> &v) {
    os << "[";
    REP(i, SZ(v)) {
        if (i) os << ", ";
        os << v[i];
    }
    return os << "]";
}

template<class T, class U>
ostream &operator<<(ostream &os, const pair<T, U> &p) {
    return os << "(" << p.first << " " << p.second << ")";
}

template<class T>
bool chmax(T &a, const T &b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

template<class T>
bool chmin(T &a, const T &b) {
    if (b < a) {
        a = b;
        return true;
    }
    return false;
}

using ll = long long;
using ull = unsigned long long;
using ld = long double;
using P = pair<int, int>;
using vi = vector<int>;
using vll = vector<ll>;
using vvi = vector<vi>;
using vvll = vector<vll>;

const ll MOD = 1e9 + 7;
const int INF = INT_MAX / 2;
const ll LINF = LLONG_MAX / 2;
const ld eps = 1e-9;


// edit

template<int64_t mod>
class modint {
    int64_t x;

public:
    modint(int64_t x = 0) : x(x < 0 ? ((x % mod) + mod) % mod : x % mod) {}

    const modint operator-() const { return x ? mod - x : 0; }

    modint &operator+=(const modint &rhs) {
        if ((x += rhs.x) >= mod) x -= mod;
        return *this;
    }

    modint &operator-=(const modint &rhs) {
        return *this += -rhs;
    }

    modint &operator*=(const modint &rhs) {
        (x *= rhs.x) %= mod;
        return *this;
    }

    modint &operator/=(const modint &rhs) {
        return *this *= rhs.pow(mod - 2);
    }

    friend const modint operator+(modint lhs, const modint &rhs) {
        return lhs += rhs;
    }

    friend const modint operator-(modint lhs, const modint &rhs) {
        return lhs -= rhs;
    }

    friend const modint operator*(modint lhs, const modint &rhs) {
        return lhs *= rhs;
    }

    friend const modint operator/(modint lhs, const modint &rhs) {
        return lhs /= rhs;
    }

    const modint pow(int64_t n) const {
        modint ret = 1, tmp = *this;
        while (n) {
            if (n & 1) ret *= tmp;
            tmp *= tmp;
            n >>= 1;
        }
        return ret;
    }

    friend bool operator==(const modint &lhs, const modint &rhs) {
        return lhs.x == rhs.x;
    }

    friend bool operator!=(const modint &lhs, const modint &rhs) {
        return !(lhs == rhs);
    }

    friend ostream &operator<<(ostream &os, const modint &a) {
        return os << a.x;
    }

    friend istream &operator>>(istream &is, modint &a) {
        int64_t tmp;
        is >> tmp;
        a = tmp;
        return is;
    }
};

using mint = modint<998244353>;

void solve() {
    int N;
    cin >> N;
    vector<int> A(N);
    REP(i, N) cin >> A[i];

    vector<mint> Lp(N);
    vector<mint> Lm(N);
    vector<mint> Rp(N);
    vector<mint> Rm(N);

    {
        int t = -1; // 前回登場した2or-2のidx
        int c = 0; // 1 or -1が連続している回数
        int s = 1; // 積の符号
        for (int i = 0; i < N; ++i) {
            if (abs(A[i]) == 2) {
                t = i;
                c = 0;
                if (i != N - 1) c++;
                s = 1;
            } else if (A[i] == 0) {
                t = -1;
                c = 0;
                s = 1;
                continue;
            } else if (abs(A[i]) == 1) {
                if (i != N - 1) c++;
                s *= A[i];
            }

            if (t == -1) {
                continue;
            }

            // 伝播
            if (s == 1) {
                mint tmp = mint(2).pow(c);
                mint inv = 1 / tmp;
                Rp[t] += inv;
            } else if (s == -1) {
                mint tmp = mint(2).pow(c);
                mint inv = 1 / tmp;
                Rm[t] += inv;
            }
        }
    }

    {
        int t = -1; // 前回登場した2or-2のidx
        int c = 0; // 1 or -1が連続している回数
        int s = 1; // 積の符号
        for (int i = N - 1; i >= 0; --i) {
            if (abs(A[i]) == 2) {
                t = i;
                c = 0;
                if (i != 0) c++;
                s = 1;
            } else if (A[i] == 0) {
                t = -1;
                c = 0;
                s = 1;
                continue;
            } else if (abs(A[i]) == 1) {
                if (i != 0) c++;
                s *= A[i];
            }
            if (t == -1) {
                continue;
            }

            // 伝播
            if (s == 1) {
                mint tmp = mint(2).pow(c);
                mint inv = 1 / tmp;
                Lp[t] += inv;
            } else if (s == -1) {
                mint tmp = mint(2).pow(c);
                mint inv = 1 / tmp;
                Lm[t] += inv;
            }
        }
    }

    mint ans = 0;
    for (int i = 0; i < N; ++i) {
        if (A[i] == 2) {
            mint tmp = Lm[i] * Rp[i] + Lp[i] * Rm[i];
//            tmp *= mint(2).pow(N - 2);
            ans += tmp;
        } else if (A[i] == -2) {
            mint tmp = Lm[i] * Rm[i] + Lp[i] * Rp[i];
//            tmp *= mint(2).pow(N - 2);
            ans += tmp;
        }
    }
    cout << ans << endl;

}


int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
//    std::ifstream in("input.txt");
//    std::cin.rdbuf(in.rdbuf());

    solve();


    return 0;
}