#include <bits/stdc++.h>
using namespace std;
template<const int MOD> struct modint{
    long long val;
    modint(): val(0) {}
    modint(long long x){
        if(x < 0) val = x % MOD + MOD;
        else val = x % MOD;
    }
    modint(const modint &t){
        val = t.val;
    }
    modint& operator =(const modint m){
        val = m.val;
        return *this;
    }
    modint operator -(){
        return modint(-val);
    }
    modint& operator-=(const modint &m){
        val -= m.val;
        if(val < 0) val += MOD;
        return *this;
    }
    modint& operator+=(const modint &m){
        val += m.val;
        if(val >= MOD) val -= MOD;
        return *this;
    }
    modint& operator*=(const modint &m){
        val *= m.val;
        val %= MOD;
        return *this;
    }
    modint& operator/=(modint m){
        *this *= m.inv();
        return *this;
    }
    modint inv(){
        long long x = 1, y = 0;
        long long a = val, b = MOD;
        while(b != 0){
            long long t = a / b;
            a -= t * b;
            x -= t * y;
            swap(a, b);
            swap(x, y);
        }
        x %= MOD;
        if(x < 0) x += MOD;
        return modint(x);
    }
    modint pow(long long k){
        long long res = 1;
        long long v = val;
        while(k > 0){
            if(k & 1) res = res * v % MOD;
            v = v * v % MOD;
            k >>= 1;
    }
        return modint(res);
    }
    bool operator==(const modint &m){
        return val == m.val;
    }
    modint operator+(const modint &m){
        return modint(*this) += m;
    }
    modint operator-(const modint &m){
        return modint(*this) -= m;
    }
    modint operator*(const modint &m){
        return modint(*this) *= m;
    }
    modint operator/(const modint &m){
        return modint(*this) /= m;
    }
    bool operator!=(const modint &m){
        return modint(*this).val != m.val;
    }
    bool operator!=(const int &m){
        return modint(*this).val != m;
    }
};
const int MOD = 998244353;
using mint = modint<MOD>;
const int MAX = 410000;
mint fac[MAX], finv[MAX], inv[MAX];
void COMinit(){
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for(int i = 2; i < MAX; i++){
        fac[i] = fac[i - 1] * i;
        inv[i] = mint(MOD) - inv[MOD % i] * (MOD / i);
        finv[i] = finv[i - 1] * inv[i];
    }
}
mint COM(int n, int k){
    if (n < k) return 0;
    if (n < 0 || k < 0) return 0;
    return fac[n] * finv[k] * finv[n - k];
}
int main(){
    int N;
    cin >> N;
    vector<int> B(N);
    for(int i = 0; i < N; i++) cin >> B[i];
    vector<vector<mint>> dp(2, vector<mint>(N));
    vector<int> cnt(300000);
    for(int i = 1; i < 300000; i++){
        int ni = 2;
        while(i >= ni){
            cnt[i] += i / ni;
            ni *= 2;
        }
    }
    for(int i = 0; i < N; i++){
        int rest = cnt[N - 1] - cnt[i] - cnt[N - 1 - i];
        if(i == 0){
            if(B[i] == -1){
                dp[0][i] = 1;
                dp[1][i] = 1;
            }
            else{
                dp[B[i]][i] = 1;
            }
        }
        else{
            if(rest > 0){
                if(B[i] == -1){
                    dp[1][i] = dp[1][i - 1] * 2;
                    dp[0][i] = dp[0][i - 1] * 2;
                }
                else{
                    dp[1][i] = dp[1][i - 1];
                    dp[0][i] = dp[0][i - 1];
                }
            }
            else{
                if(B[i] == 0){
                    dp[0][i] = dp[0][i - 1];
                    dp[1][i] = dp[1][i - 1];
                }
                else if(B[i] == 1){
                    dp[1][i] = dp[0][i - 1];
                    dp[0][i] = dp[1][i - 1];
                }
                else{
                    dp[1][i] = dp[1][i - 1] + dp[0][i - 1];
                    dp[0][i] = dp[1][i - 1] + dp[0][i - 1];
                }
            }
        }
    }
    cout << dp[1][N - 1].val << endl;
}