#include <bits/stdc++.h>

#include <atcoder/modint>
using namespace std;
using mint = atcoder::modint998244353;
void fast_io() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
}

int main() {
    fast_io();
    int n;
    cin >> n;
    vector<int> b(n);
    for (int i = 0; i < n; i++) {
        cin >> b[i];
    }
    vector<int> cnt(n);
    for (int i = 1; i < n; i++) {
        int p = 2;
        while (p <= i) {
            cnt[i] += i / p;
            p *= 2;
        }
    }
    vector<vector<mint>> dp(n + 1, vector<mint>(2, 0));
    dp[0][0] = 1;
    for (int i = 0; i < n; i++) {
        if (cnt[n - 1] > cnt[i] + cnt[n - 1 - i]) {
            if (b[i] == -1) {
                dp[i + 1][0] = 2 * dp[i][0];
                dp[i + 1][1] = 2 * dp[i][1];
            } else {
                dp[i + 1][0] = dp[i][0];
                dp[i + 1][1] = dp[i][1];
            }
        } else {
            if (b[i] == -1) {
                dp[i + 1][0] = dp[i + 1][1] = dp[i][0] + dp[i][1];
            } else if (b[i] == 0) {
                dp[i + 1][0] = dp[i][0];
                dp[i + 1][1] = dp[i][1];
            } else {
                dp[i + 1][0] = dp[i][1];
                dp[i + 1][1] = dp[i][0];
            }
        }
    }
    cout << dp[n][1].val() << endl;
}