#include <algorithm>
#include <atcoder/all>
#include <bitset>
#include <cassert>
#include <cmath>
#include <ctime>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
using namespace std;
using namespace atcoder;
typedef long long ll;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define repr(i, n) for (int i = (int)(n) - 1; i >= 0; i--)
#define repk(i, k, n) for (int i = k; i < (int)(n); i++)
#define all(v) v.begin(), v.end()
#define mod1 1000000007
#define mod2 998244353
#define mod3 100000007
#define vi vector<int>
#define vs vector<string>
#define vc vector<char>
#define vl vector<ll>
#define vb vector<bool>
#define vvi vector<vector<int>>
#define vvc vector<vector<char>>
#define vvl vector<vector<ll>>
#define vvb vector<vector<bool>>
#define vvvi vector<vector<vector<int>>>
#define vvvl vector<vector<vector<ll>>>
#define pii pair<int, int>
#define pil pair<int, ll>
#define pli pair<ll, int>
#define pll pair<ll, ll>
#define vpii vector<pair<int, int>>
#define vpll vector<pair<ll, ll>>
#define vvpii vector<vector<pair<int, int>>>
#define vvpll vector<vector<pair<ll, ll>>>

// using mint = modint998244353;

template <typename T>
void debug(T e) {
    cerr << e << endl;
}

template <typename T>
void debug(vector<T> &v) {
    rep(i, v.size()) { cerr << v[i] << " "; }
    cerr << endl;
}

template <typename T>
void debug(vector<vector<T>> &v) {
    rep(i, v.size()) {
        rep(j, v[i].size()) { cerr << v[i][j] << " "; }
        cerr << endl;
    }
}

template <typename T>
void debug(vector<pair<T, T>> &v) {
    rep(i, v.size()) { cerr << v[i].first << " " << v[i].second << endl; }
}

template <typename T>
void debug(set<T> &st) {
    for (auto itr = st.begin(); itr != st.end(); itr++) {
        cerr << *itr << " ";
    }
    cerr << endl;
}

template <typename T>
void debug(multiset<T> &ms) {
    for (auto itr = ms.begin(); itr != ms.end(); itr++) {
        cerr << *itr << " ";
    }
    cerr << endl;
}

template <typename T>
void debug(map<T, T> &mp) {
    for (auto itr = mp.begin(); itr != mp.end(); itr++) {
        cerr << itr->first << " " << itr->second << endl;
    }
}

void debug_out() { cerr << endl; }

template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
    cerr << H << " ";
    debug_out(T...);
}

using mint = modint998244353;

void debug_mint1(vector<mint> &vec) {
    for (int i = 0; i < vec.size(); i++) {
        cerr << vec[i].val() << " ";
    }
    cerr << endl;
}

void debug_mint2(vector<vector<mint>> &vec) {
    for (int i = 0; i < vec.size(); i++) {
        for (int j = 0; j < vec[i].size(); j++) {
            cerr << vec[i][j].val() << " ";
        }
        cerr << endl;
    }
}

mint op(mint a, mint b) { return a + b; }

mint e() { return mint(0); }

int main() {
    ll N;
    cin >> N;
    vector<ll> a(N);
    for (ll i = 0; i < N; i++) {
        cin >> a[i];
    }
    vector<mint> pow_2(N + 1);
    pow_2[0] = mint(1);
    for (ll i = 0; i < N; i++) {
        pow_2[i + 1] = pow_2[i] * mint(2);
    }
    segtree<mint, op, e> seg_p(N + 1);
    segtree<mint, op, e> seg_m(N + 1);
    ll rui_p = 1;
    for (ll i = 0; i < N; i++) {
        if (rui_p > 0) {
            seg_p.set(i, pow_2[N - i - 1]);
        } else {
            seg_m.set(i, pow_2[N - i - 1]);
        }
        if (a[i] < 0) {
            rui_p *= -1;
        }
    }
    if (rui_p > 0) {
        seg_p.set(N, mint(1));
    } else {
        seg_m.set(N, mint(1));
    }
    vector<ll> idx2(0);
    for (ll i = 0; i < N; i++) {
        if (abs(a[i]) == 2) {
            idx2.push_back(i);
        }
    }
    idx2.push_back(N);
    idx2.push_back(N + 1);
    vector<ll> idx0(0);
    for (ll i = 0; i < N; i++) {
        if (a[i] == 0) {
            idx0.push_back(i);
        }
    }
    idx0.push_back(N);

    mint ans = 0;
    mint now_left = mint(1);
    rui_p = 1;
    for (ll i = 0; i < N; i++) {
        auto it1 = lower_bound(all(idx2), i);
        ll id1 = *it1;
        auto it2 = lower_bound(all(idx2), id1 + 1);
        ll id2 = *it2;
        // debug_out(i, id1, id2);
        auto it0 = lower_bound(all(idx0), i);
        ll id0 = *it0;
        if (id1 > id0) {
            if (i > 0) {
                now_left *= 2;
            }
            continue;
        }
        ll p;
        if (id2 > N) {
            if (i > 0) {
                now_left *= 2;
            }
            continue;
        }
        if (rui_p == 1) {
            ans += now_left * seg_m.prod(id1 + 1, min(id0, id2) + 1);
        } else {
            ans += now_left * seg_p.prod(id1 + 1, min(id0, id2) + 1);
        }
        if (a[i] < 0) {
            rui_p *= -1;
        }
        if (i > 0) {
            now_left *= 2;
        }
        // debug(ans.val());
    }
    cout << (ans / mint(2).pow(N - 1)).val() << endl;
}