#include<bits/stdc++.h>
using namespace std;
using i64=long long;
constexpr i64 mod=998244353;
inline i64 qpow(i64 p,i64 t){
   i64 r=1;for(;t;t>>=1,p=p*p%mod)if(t&1)(r*=p)%=mod;
   return r;
}
i64 pw[300010],fac[300010],ifac[300010];
char str[300010];
int n;
inline i64 binom(int n,int m){
   return m<0||m>n?0:fac[n]*ifac[m]%mod*ifac[n-m]%mod;
}
int main(){
   scanf("%s",str+1),n=strlen(str+1);
   pw[0]=1;for(int i=1;i<=n;i++)pw[i]=pw[i-1]*2%mod;
   fac[0]=1;for(int i=1;i<=n;i++)fac[i]=fac[i-1]*i%mod;
   ifac[n]=qpow(fac[n],mod-2);for(int i=n;i;i--)ifac[i-1]=ifac[i]*i%mod;
   i64 ans=pw[n]-1;
   for(int i=1,j=1;i<=n;i++)if(i==n||str[i]!=str[i+1]){
      for(int k=j;k<=i;k++)(ans+=binom(j-1+n-k,n-k+1)+mod-binom(n,n-k+1))%=mod;
      for(int k=j;k<i;k++)(ans+=binom(j-2+n-k,j-2)*(k-j+1))%=mod;
      for(int k=j+1;k<=i;k++)(ans+=binom(k-1+n-i-1,n-i-1)*(i-k+1))%=mod;
      (ans+=binom(j-1+n-i,j-1)*(i-j+1))%=mod;
      j=i+1;
   }printf("%lld",ans);
   return 0;
}