#include <bits/stdc++.h>
using namespace std;

constexpr int mod = 998244353;
int dp[200001][2];

int main() {
    int N;
    cin >> N;
    dp[0][0] = 1;
    for(int i = 0; i < N; i++) {
        int B;
        cin >> B;
        for(int j = 0; j < 2; j++) {
            if(B == 0 || B == -1) {
                dp[i+1][j] += dp[i][j];
                dp[i+1][j] %= mod;
            }
            if(B == 1 || B == -1) {
                dp[i+1][(j+N-min(i+1,N-i))%2] += dp[i][j];
                dp[i+1][(j+N-min(i+1,N-i))%2] %= mod;
            }
        }
    }
    cout << dp[N][1] << endl;
}