#include<bits/stdc++.h>
using namespace std;
const int M = 998244353;

int main() {
    cin.tie(0);
    ios::sync_with_stdio(0);
    int n;
    cin >> n;
    vector<int> a(n);
    vector<long long> pw(n + 1);
    pw[0] = 1;
    int inv = (M + 1) / 2;
    for (int i = 0; i < n; ++i) {
        cin >> a[i];
        pw[i + 1] = pw[i] * inv % M;
    }
    long long ans = 0;
    for (int i = 0; i < n; ++i) {
        int b = 1;
        for (int j = i; j < n; ++j) {
            b *= a[j];
            if (b == -2) {
                int c = j - i + 2 - (i == 0) - (j == n - 1);
                ans = (ans + pw[c]) % M;
            }
            if (b == 0 || abs(b) > 2) break;
        }
    }
    cout << ans << '\n';
    return 0;
}