I,R=input,range
N=int(I())
A=[[0]*N for i in R(N+1)]
B=[0]*N
S=I()
P=998244353
p=[pow(2,i,P)for i in R(N)]
for i in R(1,N+1):
	s=S[N-i]>"0"
	for j in R(i):A[i][j]=B[j]=(B[j]+(S[N-i]>"0" and j>0)*(p[max(0,i-j-2)]-A[i-j-1][j])+[A[i-1][j],p[max(0,i-2)]][1>j and S[N-i]>"0"])%P
print(sum(p[j]*A[N][j]for j in R(N))%P)