#include<bits/stdc++.h>
using namespace std;
#define int long long 
const int NN=998244353;
char s[300300];
int ans;
int p[300300],ni[300300],suf[300300];
int mi(int x,int y){
	int sum=1;
	for (;y;y>>=1,x=x*x%NN)
	if(y&1)sum=sum*x%NN;
	return sum;
}
int c(int x,int y){
	if(x<0||y<0||x<y)return 0;
	return p[x]*ni[y]%NN*ni[x-y]%NN;
}
signed main(){
	scanf("%s",s+1);
	int n=strlen(s+1);
	p[0]=1;
	for (int i=1;i<=n;i++)
	p[i]=p[i-1]*i%NN;
	ni[n]=mi(p[n],NN-2);
	for (int i=n;i;i--)
	ni[i-1]=ni[i]*i%NN;
	int pre=1;
	for (int i=2;i<=n+1;i++)
	if(s[i]!=s[pre]){
		int l=pre,r=i-1;
		ans=(ans+c(l-1+n-r,l-1)*(r-l+1))%NN;
		for (int k=l;k<r;k++)
		ans=(ans+c(l-2+n-k,l-2)*(k-l+1))%NN;
		for (int k=r;k>l;k--)
		ans=(ans+c(k-1+n-r-1,n-r-1)*(r-k+1))%NN;
		for (int j=pre;j<i;j++)
		suf[j]=i;
		pre=i;
	}
	for (int i=1;i<=n;i++){
		int r=i-1+n-suf[i],l=i-1;
		ans=(ans+c(r+1,i)-c(l,i)+NN)%NN;
	}
	cout<<ans<<"\n";
}