#include <bits/stdc++.h>
using namespace std;

typedef long long ll;

const int N = 3e5 + 5;
const ll mod = 998244353;

ll fac[N << 1], ifac[N << 1];

inline void get_fac(ll n) {
	fac[0] = 1;
	for (int i = 1; i <= n; ++i) {
		fac[i] = fac[i - 1] * i % mod;
	}
	ifac[0] = ifac[1] = 1;
	for (int i = 2; i <= n; ++i) {
		ifac[i] = (mod - mod / i) * ifac[mod % i] % mod;
	}
	for (int i = 1; i <= n; ++i) {
		ifac[i] = ifac[i] * ifac[i - 1] % mod;
	}
}

inline ll C(ll n, ll m) {
	if (n < m) {
		return 0;
	}
	return fac[n] * ifac[m] % mod * ifac[n - m] % mod;
}

ll n, ans;

string s;

inline ll qpow(ll a, ll b) {
	ll res = 1;
	while (b) {
		if (b & 1) {
			res = res * a % mod;
		}
		a = a * a % mod;
		b >>= 1;
	}
	return res;
}

inline ll inv(ll a) {
	return qpow(a, mod - 2);
}

inline ll S(ll n, ll m) {
	if (m > n) {
		return 0;
	}
	return C(n + 1, m + 1);
}

int main() {
	#ifdef LOCAL
		assert(freopen("test.in", "r", stdin));
		assert(freopen("test.out", "w", stdout));
	#endif
	ios::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr);
	get_fac(6e5);
	cin >> s;
	n = s.size();
	s = "#" + s;
	ans = qpow(2, n) - 1;
	for (int i = 1; i <= n; ++i) {
		int j = i;
		while (j < n && s[j + 1] == s[j]) {
			++j;
		}
		for (int p = i - 1; p <= j - 1; ++p) {
			ans = (ans - S(n - 1, p) + S(n - j + p - 1, p) + mod) % mod;
		}
		for (int p = i; p <= j; ++p) {
			ll t = C(i - 1 + n - p, i - 1);
			if (p != j) {
				t = (t - C(i + n - p - 2, i - 1) + mod) % mod;
			}
			ans = (ans + t * (p - i + 1)) % mod;
		}
		for (int p = i + 1; p <= j; ++p) {
			ll t = C(n + p - j - 1, n - j) - C(n + p - j - 2, n - j);
			ans = (ans + t * (j - p + 1)) % mod;
		}
		i = j;
	}
	cout << ans << "\n";
	return 0;
}