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

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

long long modpow(long long a,long long b) {
    long long ans = 1;
    while(b) {
        if(b & 1) {
            (ans *= a) %= mod;
        }
        (a *= a) %= mod;
        b /= 2;
    }
    return ans;
}

int main() {
    int N;
    cin >> N;
    dp[0][0] = 1;
    int cnt = 0;
    for(int i = 0; i < N; i++) {
        int B;
        cin >> B;
        if(N%2 == 1) {
            if(i == 0 || i+1 == N) {
                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^1] += dp[i][j];
                        dp[i+1][j^1] %= mod;
                    }
                }
            }
            else {
                if(B == -1) {
                    cnt++;
                }
                for(int j = 0; j < 2; j++) {
                    dp[i+1][j] = dp[i][j];
                }
            }
        }
        if(N%2 == 0) {
            if(i <= N/4*2 || i+N/4*2 >= N) {
                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^1] += dp[i][j];
                        dp[i+1][j^1] %= mod;
                    }
                }
            }
            else {
                if(B == -1) {
                    cnt++;
                }
                for(int j = 0; j < 2; j++) {
                    dp[i+1][j] = dp[i][j];
                }
            }
        }
    }
    cout << modpow(2,cnt)*dp[N][1]%mod << endl;
}