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