#include <iostream>
#include <vector>
#include <atcoder/modint>

namespace ac = atcoder;
using mint = ac::modint998244353;

void solve() {
    int n;
    std::cin >> n;

    std::vector<int> xs(n);
    for (auto& x : xs) std::cin >> x;

    std::vector<mint> inv2(n + 1, 0);
    inv2[n] = mint(2).pow(n).inv();
    for (int i = n - 1; i >= 0; --i) inv2[i] = inv2[i + 1] * 2;

    mint ans = 0;
    for (int s = 0; s < n; ++s) {
        if (std::abs(xs[s]) != 2) continue;

        std::vector<mint> left(2, 0);
        {
            int sign = 0, bar = (s > 0);
            left[sign] = inv2[bar];
            for (int i = s - 1; i >= 0 && std::abs(xs[i]) == 1; --i) {
                if (xs[i] < 0) sign = 1 - sign;
                if (i > 0) ++bar;
                left[sign] += inv2[bar];
            }
        }

        std::vector<mint> right(2, 0);
        {
            int sign = (xs[s] < 0), bar = (s < n - 1);
            right[sign] = inv2[bar];
            for (int i = s + 1; i < n && std::abs(xs[i]) == 1; ++i) {
                if (xs[i] < 0) sign = 1 - sign;
                if (i < n - 1) ++bar;
                right[sign] += inv2[bar];
            }
        }

        ans += left[0] * right[1] + left[1] * right[0];
    }

    std::cout << ans.val() << "\n";
}

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

    solve();

    return 0;
}