#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) {
        if (abs(a[i]) < 2) continue;
        int al = 1;
        for (int l = i; l >= 0; --l) {
            if (l < i) al *= a[l];
            if (abs(al) != 1) break;
            int ar = 1;
            for (int r = i; r < n; ++r) {
                if (i < r) ar *= a[r];
                if (abs(ar) != 1) break;
                if (a[i] * al * ar == -2) {
                    ans = (ans + pw[r - l + 2 - (l == 0) - (r == n - 1)]) % M;
                }
            }
        }
    }
    cout << ans << '\n';
    return 0;
}