#include <bits/stdc++.h>
using namespace std;
const long long MOD = 998244353;
int main(){
  int N;
  cin >> N;
  vector<int> B(N);
  for (int i = 0; i < N; i++){
    cin >> B[i];
  }
  vector<int> c(N);
  for (int i = 0; i < N; i++){
    if (((N - 1) & i) == i){
      c[i] = 1;
    } else {
      c[i] = 0;
    }
  }
 vector<vector<long long>> dp(N + 1, vector<long long>(2, 0));
  dp[0][0] = 1;
  for (int i = 0; i < N; i++){
    for (int j = 0; j < 2; j++){
      if (B[i] != 1){
        dp[i + 1][j] += dp[i][j];
        dp[i + 1][j] %= MOD;
      }
      if (B[i] != 0){
        dp[i + 1][j ^ c[i]] += dp[i][j];
        dp[i + 1][j ^ c[i]] %= MOD;
      }
    }
  }
  cout << dp[N][1] << endl;
}