#include<stdio.h>
char s[500009];int i,l;long p=1;main(){scanf("%*d%s",s);for(i=1;s[i-1];i++)s[i]<s[i-1]&&(p=p*(~s[l]&s[i-1]&1?i-l+1:1)%998244353,l=i);printf("%ld",p);}