#include <iostream>
using namespace std;
typedef long long ll;

const ll MOD = 998244353;

int main()
{
    int n;
    cin >> n;
    int b[200005];
    for(int i = 0; i < n; i++) cin >> b[i];
    ll dp[2]{0};
    dp[0] = 1;
    for(int i = 0; i < n; i++){
        ll d[2]{0};
        if(((n - 1) & i) == i){
            if(b[i] == 0) d[0] = dp[0], d[1] = dp[1];
            if(b[i] == 1) d[0] = dp[1], d[1] = dp[0];
            if(b[i] == -1) d[0] = (dp[0] + dp[1]) % MOD, d[1] = (dp[0] + dp[1]) % MOD;
        }
        else{
            if(b[i] != -1) d[0] = dp[0], d[1] = dp[1];
            else d[0] = dp[0] * 2 % MOD, d[1] = dp[1] * 2 % MOD;
        }
        swap(d, dp);
    }
    cout << dp[1] << endl;
}