#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll _=3e5+5,M=998244353;
ll n,t,s,b[_],d[_],e[_],i,j,g;string a;
inline ll qp(ll x,ll y){ll z=1;for(;y;y>>=1,x=x*x%M)if(y&1)z=z*x%M;return z;}
inline ll C(ll x,ll y){return (y<0||x-y<0)?0:d[x]*e[y]%M*e[x-y]%M;}
int main(){
	ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
	for(d[0]=i=1;i<_;i++)d[i]=d[i-1]*i%M;
	for(i=_-1,e[i]=qp(d[i],M-2);i;i--)e[i-1]=e[i]*i%M;
	for(b[0]=i=1;i<_;i++)b[i]=b[i-1]*2%M;
	for(i=0;i<_;i++)b[i]=(M-b[i]+1+i)%M;
	cin>>a;n=a.size();a=' '+a;s=qp(2,n)-1;
	for(i=j=n;i;i--)if(a[i]!=a[i-1]){
		t=j-i+1;
		(s+=b[t]*C(n-t,i-1))%=M;
		for(g=1;g<t;g++)(s+=b[g]*(C(n-g-1,i-2)+C(n-g-1,n-j-1)))%=M;
		j=i-1;
	}
	cout<<s<<'\n';
}