#include<bits/stdc++.h>
#define ll int
#define N 1005
#define mod 998244353
using namespace std;
ll n,i,f[N][N][2],g[N][N][2],h[N][N],j,k,ans,dw,up;
char s[N];
inline void add(ll &x,ll y){(x+=y)>=mod&&(x-=mod);}
int main(){
	ios::sync_with_stdio(false);
	cin>>n>>(s+1);
	reverse(s+1,s+n+1);
	f[0+n][0+n][0] = 1;
	for(i=1;i<=n;i++){
		if(s[i]!='1'){
			for(j=dw;j<=up;j++){
				for(k=dw;k<=0;k++){
					if(!f[j+n][k+n][0]&&!f[j+n][k+n][1]) continue;
					add(g[j+1+n][k+n][0],f[j+n][k+n][0]);
					add(g[j+1+n][k+n][0],f[j+n][k+n][1]);
				}
			}
		}
		if(s[i]!='0'&&i!=n&&i!=1&&i!=2){
			for(j=dw;j<=up;j++){
				for(k=dw;k<=0;k++){
					if(!f[j+n][k+n][0]) continue;
					if(k-j+3>=2) continue;
					add(g[j-3+n][min(k,j-3)+n][1],f[j+n][k+n][0]);
				}
			}
		}
		if(s[i]=='?'||s[i]=='1') dw=max(-n,max(dw-3,(i+1)/2*(-3)));
		if(s[i]=='?'||s[i]=='0') up=min(n,up+1);
		for(j=dw;j<=up;j++) for(k=dw;k<=0;k++) f[j+n][k+n][0]=g[j+n][k+n][0],f[j+n][k+n][1]=g[j+n][k+n][1],g[j+n][k+n][0]=g[j+n][k+n][1]=0;
	}
	for(i=-n;i<=0;i++) add(ans,f[0+n][i+n][0]);
	cout<<ans<<endl;
	return 0;
}