#pragma GCC target ("avx2")
#pragma GCC optimize ("O3")
#pragma GCC optimize("Ofast")
#pragma GCC optimize ("unroll-loops")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
using namespace std;
#define io ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL) 
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define endl '\n'
typedef long long ll;
// #define mod1 (ll)1000000007
#define mod2 (ll)998244353
#define pll pair<ll,ll>
typedef long double lb;
typedef tree<
pair<ll, ll>,
null_type,
less<pair<ll, ll>>,
rb_tree_tag,
tree_order_statistics_node_update> ordered_set;
#define eps (lb)(1e-9)
struct custom_hash {
    static uint64_t splitmix64(uint64_t x) {
        x += 0x9e3779b97f4a7c15;
        x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
        x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
        return x ^ (x >> 31);
    }

    size_t operator()(uint64_t x) const {
        static const uint64_t FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count();
        return splitmix64(x + FIXED_RANDOM);
    }
};
// Operator overloads
template<typename T1, typename T2> // cin >> pair<T1, T2>
istream& operator>>(istream &istream, pair<T1, T2> &p) { return (istream >> p.first >> p.second); }

template<typename T> // cin >> vector<T>
istream& operator>>(istream &istream, vector<T> &v)
{
    for (auto &it : v)
        cin >> it;
    return istream;
}

template<typename T1, typename T2> // cout << pair<T1, T2>
ostream& operator<<(ostream &ostream, const pair<T1, T2> &p) { return (ostream << p.first << " " << p.second); }
template<typename T> // cout << vector<T>
ostream& operator<<(ostream &ostream, const vector<T> &c) { for (auto &it : c) cout << it << " "; return ostream; }

// Utility functions
template <typename T>
void print(T &&t)  { cout << t << "\n"; }
template <typename T, typename... Args>
void print(T &&t, Args &&... args)
{
    cout << t << " ";
    print(forward<Args>(args)...);
}
mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
ll random(ll p){ // gives random number in [0,p]

 return uniform_int_distribution<ll>(0, p)(rng);
}
ll n;
vector<ll>v;
ll mod=mod2;
ll mod1=mod2;
ll dp[4000][4000];
ll sum[4000][4000];
ll pwr[5000];
ll power(ll a, ll b, ll c=mod1){
     if(a==0){
         return 0;}
     else if(b==0||a==1){
         return 1;}
     ll p=power(a,b/2,c);
     p*=p; p%=c;
     if(b%2){p*=a;} p%=c;
     return p;}
ll modinv(ll a, ll c=mod1){
     return power(a,c-2,c);
}
const ll MAXN =1000000;
ll fac[MAXN+1];
ll invfac[MAXN+1];
void factorial(ll mod=mod1){
    fac[0]=1;
    for(ll i(1);i<=MAXN;++i){fac[i]=i*fac[i-1]; fac[i]%=mod;}
    invfac[MAXN]=modinv(fac[MAXN],mod);
    for(ll i(MAXN-1);i>-1;--i)
    {
        invfac[i]=(i+1ll)*invfac[i+1];
        invfac[i]%=mod;
    }
    for(ll i(0);i<5000;++i){
        pwr[i]=power(2,i);
    }
}
ll C(ll n,ll r,ll mod=mod1){
    if(n<0||r<0||r>n){return 0;}
    ll p=fac[n]; ll q=invfac[n-r]*invfac[r];  q%=mod;
    p*=q; p%=mod;
    return p;
}
void pre(){
    for(ll j(0);j<n;++j){
        ll rs=0;
        for(ll i(0);i<n;++i){
            if(j>i){
                dp[i][j]=0;
            }
            else if(j==i){
                dp[i][j]=(v[0]==1);
            }
            else if(v[i-j]==0){
                dp[i][j]=sum[i-1][j];
            }
            else{
                dp[i][j]=pwr[i-j];
                if(j>0){
                    dp[i][j]+=(sum[i-1][j]-sum[i-j-1][j]);
                }
            }
            rs+=dp[i][j];
            rs%=mod;
            sum[i][j]=rs;
        }
    }
}
void solve();
int main() {
io;
ll t=1,n=1;
// cin>>t;
factorial();
while (t--){
     solve();
    }
     return 0;
}
void solve(){
    cin>>n;
    v.resize(n);
    for(ll i(0);i<n;++i){
        char p; cin>>p;
        v[i]=p-'0';
    }
    pre();
    ll ans=0;
    for(ll i(0);i<n;++i){
        ll c=power(2,i);
        ans+=c*dp[n-1][i];
        ans%=mod;
    }
    cout<<ans<<endl;




}
// Do not get stuck on a single approach for long, think of multiple ways