#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
using namespace std;
using std::cout;
using std::cin;
using std::endl;
using ll=long long;
using ld=long double;
ll ILL=167167167167167167;
const int INF=2100000000;
const ll mod=998244353;
#define rep(i,a) for (ll i=0;i<a;i++)
#define all(p) p.begin(),p.end()
template<class T> using _pq = priority_queue<T, vector<T>, greater<T>>;
template<class T> ll LB(vector<T> &v,T a){return lower_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> ll UB(vector<T> &v,T a){return upper_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> bool chmin(T &a,const T &b){if(a>b){a=b;return 1;}else return 0;}
template<class T> bool chmax(T &a,const T &b){if(a<b){a=b;return 1;}else return 0;}
template<class T> void So(vector<T> &v) {sort(v.begin(),v.end());}
template<class T> void Sore(vector<T> &v) {sort(v.begin(),v.end(),[](T x,T y){return x>y;});}
void yneos(bool a){if(a) cout<<"Yes\n"; else cout<<"No\n";}
template<class T> void vec_out(vector<T> &p){for(int i=0;i<(int)(p.size());i++){if(i) cout<<" ";cout<<p[i];}cout<<"\n";}

ll jyo(ll x,ll y,ll z){
  ll H=y; //ここから
       ll a=1,b=(x%z+z)%z,c=1;
       while(H>0){
         a*=2;
         if(H%a!=0){
           H-=a/2;
           c*=b;
           c%=z;
         }
        b*=b;
         b%=z;
      } //ここまで
 return c;
}


namespace po167{
struct combination{
	int upper;
	long long MOD;
	std::vector<long long> fact;
	std::vector<long long> rev;
	std::vector<long long> fact_rev;
	combination(int max,long long mod):upper(max),MOD(mod),fact(max+1),rev(max+1),fact_rev(max+1){
		for(long long i=0;i<=max;i++){
			if(i<2){
				fact[i]=1;
				fact_rev[i]=1;
				rev[i]=1;
				continue;
			}
			fact[i]=(fact[i-1]*i)%mod;
			rev[i]=mod-((mod/i)*rev[mod%i])%mod;
			fact_rev[i]=(fact_rev[i-1]*rev[i])%mod;
		}
	}
	long long Comb(int x,int y){
		assert(upper>=x);
		if (x<y||y<0||x<0) return 0;
		return (((fact_rev[y]*fact_rev[x-y])%MOD)*fact[x])%MOD;
	}
};
}
using po167::combination;


void solve();
// oddloop
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	
	int t=1;
	//cin>>t;
	rep(i,t) solve();
}

void solve(){
	int N;
	cin>>N;
	string S;
	cin>>S;
	N++;
	S=S+"1";
	vector<ll> dp0(N*4),dp1(N*4);
	dp1[N*2]=1;
	ll ans=1;
	rep(i,N){
		vector<ll> n_dp0(N*4),n_dp1(N*4);
		if(S[i]=='0') ans=0;
		rep(k,N*4){
			dp0[k]%=mod;
			dp1[k]%=mod;
			if(dp0[k]+dp1[k]==0) continue;
			if(S[i]!='0'){
				n_dp1[k]+=dp0[k]+dp1[k];
			}
			if(S[i]!='1'){
				n_dp0[k+1]+=dp1[k];
				n_dp0[k-1]+=dp0[k];
			}
		}/*
		vec_out(dp0);
		vec_out(dp1);*/
		swap(n_dp0,dp0);
		swap(n_dp1,dp1);
	}
	rep(k,N*4){
		if(k>N*2&&k%2==0) ans=(ans+dp1[k])%mod;
	}
	cout<<ans<<"\n";
}