#include<bits/stdc++.h>
namespace {
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunused-function"
#include<atcoder/all>
#pragma GCC diagnostic pop
using namespace std;
using namespace atcoder;
#define rep(i,n)for (int i = 0; i < int(n); ++i)
#define rrep(i,n)for (int i = int(n)-1; i >= 0; --i)
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
template<class T> void chmax(T& a, const T& b) { a = max(a, b); }
template<class T> void chmin(T& a, const T& b) { a = min(a, b); }
using ll = long long;
using P = pair<int,int>;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;
using mint = modint998244353;

} int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n;
  cin >> n;
  VI b(n);
  rep(i, n) cin >> b[i];
  int f = 0, cnt = 0;
  mint coeff = 1;
  rep(i, n) {
    if ((i & (n - 1)) == i) {
      if (b[i] == 1) f ^= 1;
      else if (b[i] == -1) cnt++;
    } else {
      if (b[i] == -1) coeff *= 2;
    }
  }
  if (cnt == 0) {
    if (!f) coeff = 0;
  } else cnt--;
  mint ans = coeff * mint(2).pow(cnt);
  cout << ans.val() << endl;
}