// created:  2024-09-11 14:12:51
#include<cstdio>
#include<cctype>
#include<type_traits>
#define F(i,l,r) for(int i=(l),i##_end=(r);i<i##_end;++i)
#define I128 //||is_same<T,__int128_t>::value||is_same<T,__uint128_t>::value
using namespace std;
template<typename T>enable_if_t<is_integral<T>::value I128,void> readmain(T &x)
{
	bool neg=false;int c=getchar();
	for(;!isdigit(c);c=getchar())if(c=='-')neg=true;
	for(x=0;isdigit(c);c=getchar())x=(T)(10*x+(c-'0'));
	if(neg)x=-x;
}
template<typename T>T& read(T &x){readmain(x);return x;}
template<typename T,typename ...Tr>void read(T &x,Tr&... r){readmain(x);read(r...);}
typedef unsigned long long ull;
constexpr int N=3e5+5,MOD=998244353;
void reduce(int &x){(x>=MOD)&&(x-=MOD);}
int qpow(ull a,int b,ull c=1)
{
	for(;b;b>>=1,(a*=a)%=MOD)if(b&1)(c*=a)%=MOD;
	return (int)c;
}
int p2[N],fac[N],invfac[N];
int bn(int n,int m){return (int)((ull)fac[n+m]*invfac[n]%MOD*invfac[m]%MOD);}
int n,ans;
char s[N];
int main()
{
	F(i,p2[0]=1,N)reduce(p2[i]=p2[i-1]<<1);
	F(i,fac[0]=1,N)fac[i]=(int)((ull)fac[i-1]*i%MOD);
	invfac[N-1]=qpow(fac[N-1],MOD-2);
	for(int i=N;--i;)invfac[i-1]=(int)((ull)invfac[i]*i%MOD);
	scanf("%s",s);
	while(s[n])++n;
	ans=p2[n]-1;
	for(int l=0,r=0;l<n;l=r)
	{
		while(s[l]==s[r])++r;
		ans=(int)((ans+(ull)bn(l,n-r)*(MOD-p2[r-l]+(r-l)+1))%MOD);
		if(r<n)F(i,l+1,r)ans=(int)((ans+(ull)bn(i,n-r-1)*(MOD-p2[r-i]+(r-i)+1))%MOD);
		if(l)F(i,l+1,r)ans=(int)((ans+(ull)bn(l-1,n-i)*(MOD-p2[i-l]+(i-l)+1))%MOD);
	}
	printf("%d\n",ans);
	return 0;
}