# coding: utf-8
# Your code here!
N=int(input())
S=input()

MOD=998244353

if "1" not in S:
    print(0)
    exit()

ans=1
count=-1
for s in S:
    if s=="1":
        if count==-1:
            count=0
        else:
            ans*=(count+2)
            ans%=MOD
            count=0
    else:
        if count==-1:
            pass
        else:
            count+=1

print(ans)