#include<bits/stdc++.h>
using namespace std;
constexpr int M=3e5+5,mod=998244353;
string str;int n,ans,pw[M],fac[M],ifac[M];
int c(int n,int m){return 1ll*fac[n]*ifac[n-m]%mod*ifac[m]%mod;}
int qpow(int x,int n){
	int s=1; while (n){
		if (n&1) s=1ll*s*x%mod;
		x=1ll*x*x%mod; n>>=1;
	} return s;
}
int rdc(int x){return x>=mod?x-mod:x;}
int main(){
	ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
	cin>>str;n=str.length();str=" "+str;
	for (int i=fac[0]=1;i<=n;i++) fac[i]=1ll*fac[i-1]*i%mod;
	ifac[n]=qpow(fac[n],mod-2);
	for (int i=n;i;i--) ifac[i-1]=1ll*ifac[i]*i%mod;
	ans=1; for (int i=1;i<=n;i++) ans=rdc(ans<<1); ans--;
	for (int i=1,j;i<=n;i=j+1){
		j=i;while (j<=n&&str[i]==str[j]) j++; j--;
		ans=(ans+1ll*c(i-1+n-j,i-1)*(j-i+1))%mod;
		for (int r=i;r<=j;r++){
			ans=rdc(ans+mod-c(n,r));
			if (i>1) ans=rdc(ans+c(i+n-r-1,n-r+1));
		}
		for (int k=i;k<j;k++) ans=(ans+1ll*c(i-2+n-k,i-2)*(k-i+1))%mod;
		for (int k=i+1;k<=j;k++) ans=(ans+1ll*c(k-2+n-j,n-j-1)*(j-k+1))%mod;
	}
	printf("%d\n",ans);
	return 0;
}