#include <bits/stdc++.h>
using namespace std;
const long long MOD = 998244353;
const long long INV = 499122177;
long long modpow(long long a, long long b){
	long long ans = 1;
	while (b > 0){
		if (b % 2 == 1){
			ans *= a;
			ans %= MOD;
		}
		a *= a;
		a %= MOD;
		b /= 2;
	}
	return ans;
}
long long modinv(long long a){
	return modpow(a, MOD - 2);
}
vector<long long> ntt(vector<long long> A, bool inv){
	int N = A.size();
	long long r = 3;
	if (inv){
		r = modinv(r);
	}
	vector<long long> B(N);
	for (int i = N / 2; i > 0; i /= 2){
		long long z = modpow(r, (MOD - 1) / (N / i));
		long long z2 = 1;
		for (int j = 0; j < N; j += i * 2){
			for (int k = 0; k < i; k++){
				A[i + j + k] *= z2;
				A[i + j + k] %= MOD;
				B[j / 2 + k] = (A[j + k] + A[i + j + k]) % MOD;
				B[N / 2 + j / 2 + k] = (A[j + k] - A[i + j + k] + MOD) % MOD;
			}
			z2 = z2 * z % MOD;
		}
		swap(A, B);
	}
	if (inv){
		int Ninv = modinv(N);
		for (int i = 0; i < N; i++){
			A[i] = A[i] * Ninv % MOD;
		}
	}
	return A;
}
vector<long long> convolution(vector<long long> A, vector<long long> B, int d = -1){
	int deg = A.size() + B.size() - 1;
	int N = 1;
	while (N < deg){
		N *= 2;
	}
	A.resize(N);
	B.resize(N);
	A = ntt(A, false);
	B = ntt(B, false);
	vector<long long> ans(N);
	for (int i = 0; i < N; i++){
		ans[i] = A[i] * B[i] % MOD;
	}
	ans = ntt(ans, true);
	if (d != -1){
		deg = d;
	}
	ans.resize(deg);
	return ans;
}
int main(){
  int N;
  cin >> N;
  vector<int> a(N + 2, 0);
  for (int i = 1; i <= N; i++){
    cin >> a[i];
  }
  N += 2;
  vector<long long> pow(N);
  pow[0] = 1;
  for (int i = 1; i < N; i++){
    pow[i] = pow[i - 1] * INV % MOD;
  }
  long long ans = 0;
  for (int i = 0; i < N; i++){
    if (abs(a[i]) == 2){
      vector<long long> L1, L2;
      L1.push_back(0);
      L2.push_back(0);
      int p = 1;
      for (int j = i - 1; j >= 0; j--){
        if (abs(a[j]) == 1){
          p *= a[j];
          if (p == 1){
            L1.push_back(1);
            L2.push_back(0);
          } else {
            L1.push_back(0);
            L2.push_back(1);
          }
        } else {
          break;
        }
      }
      vector<long long> R1, R2;
      R1.push_back(0);
      R2.push_back(0);
      p = 1;
      for (int j = i + 1; j < N; j++){
        if (abs(a[j]) == 1){
          p *= a[j];
          if (p == 1){
            R1.push_back(1);
            R2.push_back(0);
          } else {
            R1.push_back(0);
            R2.push_back(1);
          }
        } else {
          break;
        }
      }
      if (a[i] == 2){
        vector<long long> C1 = convolution(L1, R2);
        int sz1 = C1.size();
        for (int j = 0; j < sz1; j++){
          ans += C1[j] * pow[j + 2] % MOD;
          ans %= MOD;
        }
        vector<long long> C2 = convolution(L2, R1);
        int sz2 = C2.size();
        for (int j = 0; j < sz2; j++){
          ans += C2[j] * pow[j + 2] % MOD;
          ans %= MOD;
        }
      } else {
        L1[0] = 1;
        R1[0] = 1;
        vector<long long> C1 = convolution(L1, R1);
        int sz1 = C1.size();
        for (int j = 0; j < sz1; j++){
          ans += C1[j] * pow[j + 2] % MOD;
          ans %= MOD;
        }
        vector<long long> C2 = convolution(L2, R2);
        int sz2 = C2.size();
        for (int j = 0; j < sz2; j++){
          ans += C2[j] * pow[j + 2] % MOD;
          ans %= MOD;
        }
        ans %= MOD;
      }
    }
  }
  int prod = 1;
  for (int i = 1; i < N - 2; i++){
    prod *= a[i];
    if (prod == -2){
      ans += MOD - pow[i + 1];
      ans += pow[i];
    } else if (abs(prod) > 2 || prod == 0){
      break;
    }
  }
  prod = 1;
  for (int i = N - 2; i >= 1; i--){
    prod *= a[i];
    if (prod == -2){
      if (i > 1){
        ans += MOD - pow[N - i];
        ans += pow[N - 1 - i];
      } else {
        ans += MOD - pow[N - i];
        ans += pow[N - 2 - i];
      }
    } else if (abs(prod) > 2 || prod == 0){
      break;
    }
  }
  ans %= MOD;
  cout << ans << endl;
}