#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")

#include <algorithm>
#include <bitset>
#include <climits>
#include <cmath>
#include <cstring>
#include <deque>
#include <forward_list>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <queue>
#include <set>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;
typedef long long ll;
typedef pair<int, int> P;
typedef bitset<16> BS;

const ll MOD = 998244353;
const ll INF = 1E18;
const int MAX_N = 2E+05;

int N;

ll A[MAX_N + 1], L[MAX_N + 1][2], R[MAX_N + 1][2];

ll modPow(ll x, ll a);

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

    cin >> N;

    for (int i = 1; i <= N; i++) {
        cin >> A[i];
    }

    for (int i = 1; i <= N;) {
        if (A[i] == 2 || A[i] == -2) {
            int j = i, res = 1;
            while (true) {
                if (res == -1) {
                    R[i][0] += modPow(2, max(0, N - j - 1));
                    R[i][0] %= MOD;
                } else {
                    R[i][1] += modPow(2, max(0, N - j - 1));
                    R[i][1] %= MOD;
                }
                j++;
                res *= A[j];
                if (!(A[j] == 1 || A[j] == -1) || j > N)
                    break;
            }
            i = j;
        } else {
            i++;
        }
    }

    for (int i = N; i >= 1;) {
        if (A[i] == 2 || A[i] == -2) {
            int j = i, res = 1;
            while (true) {
                if (res == -1) {
                    L[i][0] += modPow(2, max(0, j - 2));
                    L[i][0] %= MOD;
                } else {
                    L[i][1] += modPow(2, max(0, j - 2));
                    L[i][1] %= MOD;
                }
                j--;
                res *= A[j];
                if (!(A[j] == 1 || A[j] == -1) || j < 1)
                    break;
            }
            i = j;
        } else {
            i--;
        }
    }
    /*
    for (int i = 1; i <= N; i++) {
        cout << "i = " << i << ", L0 = " << L[i][0] << ", L1 = " << L[i][1] << "\n";
    }
    for (int i = 1; i <= N; i++) {
        cout << "i = " << i << ", R0 = " << R[i][0] << ", R1 = " << R[i][1] << "\n";
    }
    */

    ll ans = 0;
    for (int i = 1; i <= N; i++) {
        if (A[i] == 2) {
            ll res = L[i][1] * R[i][0] + L[i][0] * R[i][1];
            res %= MOD;
            ans += res;
            ans %= MOD;
        } else if (A[i] == -2) {
            ll res = L[i][0] * R[i][0] + L[i][1] * R[i][1];
            res %= MOD;
            ans += res;
            ans %= MOD;
        }
        //cout << "i = " << i << ", ans = " << ans << "\n";
    }
    ll Q = modPow(2, N - 1);
    Q = modPow(Q, MOD - 2);
    ans *= Q;
    ans %= MOD;

    /*
    for (int i = 0; i < N; i++) {
        for (int j = 0; j < N; j++) {
            cout << "i = " << i << ", j = " << j << ", dp = " << dp[i][j] << "\n";
        }
    }
    */

    cout << ans << "\n";

    return 0;
}

ll modPow(ll x, ll a)
{
    ll ans = 1;
    while (a > 0) {
        if (a & 1) {
            ans = (ans * x) % MOD;
        }
        x = (x * x) % MOD;
        a >>= 1;
    }
    return ans;
}