#include<bits/stdc++.h>
using namespace std;
using ll = long long;
const ll mod = 998'244'353;
//const ll mod = 1'000'000'007;
//const ll mod = 67'280'421'310'721;
struct mint{
    long long x;
    mint(long long x=0):x((x%mod+mod)%mod){}
    mint operator-() const{
        return mint(-x);
    }
    mint& operator+=(const mint& a){
        if((x+=a.x)>=mod)x-=mod;
        return *this;
    }
    mint& operator-=(const mint& a){
        if((x+=mod-a.x)>=mod)x-=mod;
        return *this;
    }
    mint& operator*=(const  mint& a){
        (x *= a.x) %= mod;
        return *this;
    }
    mint operator+(const mint& a) const{
        mint res(*this);
        return res+=a;
    }
    mint operator-(const mint& a) const{
        mint res(*this);
        return res-=a;
    }
    mint operator*(const mint& a) const{
        mint res(*this);
        return res*=a;
    }
    mint pow(long long n) const {
        assert(0 <= n);
        mint a = *this, r = 1;
        while (n) {
            if (n & 1) r *= a;
            a *= a;
            n >>= 1;
        }
        return r;
    }
    mint inv() const{
        return pow(mod-2);
    }
    mint& operator/=(const mint& a){
        return (*this)*=a.inv();
    }
    mint operator/(const mint& a) const {
        mint res(*this);
        return res/=a;
    }
    friend ostream& operator<<(ostream& os, const mint& m){
        os << m.x;
        return os;
    }
    bool operator==(const mint& a) const {
        return x == a.x;
    }
    bool operator<(const mint& a) const{
        return x < a.x;
    }
};


int main(){
    int n;
    cin>>n;
    vector<int> a(n);
    for(int i = 0;i<n;i++) cin>>a[i];
    vector<vector<mint > > dp(n,vector<mint>(2,0));
    if(a[0]==0) dp[0][0] += 1;
    else if(a[0]==1) dp[0][1] += 1;
    else{
        dp[0][0] += 1;
        dp[0][1] += 1;
    }
    for(int i = 1;i<n;i++){
        if((i&(n-1))==i){
            if(a[i]==-1){
                dp[i][0] = dp[i-1][0] + dp[i-1][1];
                dp[i][1] = dp[i-1][0] + dp[i-1][1];
            }else{
                dp[i][0] = dp[i-1][0^a[i]];
                dp[i][1] = dp[i-1][1^a[i]];
            }
        }else{
            if(a[i]==-1){
                dp[i][0] = mint(2) * dp[i-1][0];
                dp[i][1] = mint(2) * dp[i-1][1];
            }else{
                dp[i][0] = dp[i-1][0];
                dp[i][1] = dp[i-1][1];
            }
        }
    }
    cout<<dp[n-1][1]<<endl;


}