#include <bits/stdc++.h>
using namespace std;
const int P = 998244353; 
const int N = 3e5 + 5; 

inline int poww(int a, int b) {
    int r = 1; 
    for (; b; b >>= 1, a = 1ll * a * a % P) if (b & 1) r = 1ll * r * a % P; 
    return r; 
}

int n, fac[N], ifac[N]; 
char a[N]; 

inline void initFac(void) {
    for (int i = fac[0] = 1; i < N; ++i) fac[i] = 1ll * fac[i - 1] * i % P; 
    ifac[N - 1] = poww(fac[N - 1], P - 2); 
    for (int i = N - 2; i >= 0; --i) ifac[i] = 1ll * ifac[i + 1] * (i + 1) % P; 
}
inline int C(int n, int m) {
    if (n < m || n < 0 || m < 0) return 0; 
    return 1ll * fac[n] * ifac[m] % P * ifac[n - m] % P; 
}

int main(void) {
    initFac(); 
    ios::sync_with_stdio(0); 
    cin >> a + 1; n = strlen(a + 1); 
    int ans = poww(2, n) - 1; 
    for (int l = 1, r; l <= n; l = r + 1) {
        r = l; 
        while (r < n && a[r + 1] == a[l]) ++r; 
        int t = r - l + 1; 
        if (t > 1) ans = (ans - 1ll * C(n - t, l - 1) * (poww(2, t) - 1 - t)) % P; 
        for (int i = l + 1; i < r; ++i) {
            int t = i - l + 1; 
            ans = (ans - 1ll * C(n - t - 1, l - 2) * (poww(2, t) - 1 - t)) % P; 

            t = r - i + 1; 
            ans = (ans - 1ll * C(n - t - 1, n - r - 1) * (poww(2, t) - 1 - t)) % P; 
        }
        // cerr << l << " " << r << "\n"; 
    }
    cout << (ans + P) % P << "\n"; 
    return 0;
}