#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const ll MOD = 998244353;
using P = pair<int,int>;
#define rep(i, n) for(int i = 0; i < n; i++)
#define all(x) (x).begin(),(x).end()
const int MAX_N = 200200;
vector<ll> fac(MAX_N), finv(MAX_N), inv(MAX_N);
void mcomin(){
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for(int i=2;i<MAX_N;i++){
        fac[i] = fac[i-1] * i % MOD;
        inv[i] = MOD - inv[MOD%i] * (MOD/i) % MOD;
        finv[i] = finv[i-1] * inv[i] % MOD;
    }
}
ll mcomb(int n,int k){
    if (n<k) return 0;
    if (n<0 || k<0) return 0;
    return fac[n] * (finv[k] * finv[n-k] % MOD) % MOD;
}
ll mpow(ll x, ll y){
    ll res = 1; x %= MOD;
    while(y){
        if(y%2) res = res * x % MOD;
        x = x * x % MOD;
        y /= 2;
    }
    return res;
}
int main(){
    mcomin();
    int n;
    cin >> n;
    vector<int> b(n);
    rep(i,n) cin >> b[i];
    ll even = 0, num1 = 0, num0 = 0, p = n, q = 0, k = 0;
    rep(i,n){
        if(q){
            ll pp = p, qq = q;
            while(!(pp%2)){
                pp /= 2;
                even++;
            }
            while(!(qq%2)){
                qq /= 2;
                even--;
            }
        }
        if(b[i] == -1){
            if(even) num0++;
            else num1++;
        }else if(b[i] == 1 && !even) k = k^1;
        p--; q++;
    }
    ll ans = 0;
    for(ll i=(k==0);i<=num1;i+=2){
        ans += mcomb(num1,i);
    }
    ans %= MOD;
    ans = ans * mpow(2,num0) % MOD;
    cout << ans << endl;
    return 0;
}