#include<bits/stdc++.h>
#include<atcoder/all>
#define fast std::ios::sync_with_stdio(false); std::cin.tie(nullptr); std::cout.tie(nullptr)
#define eb emplace_back
#define all(x) (x).begin(), (x).end()
using namespace std;
using ll = long long;
using mint = atcoder::modint998244353;
constexpr ll inf = 2e18;
constexpr int mod = 998244353;
#ifdef LOCAL
#define debug(x) std::cerr << #x << " = " << (x) << std::endl;
#else
#define debug(x) 
#endif
static void judge(bool c) {
    std::cout << (c ? "Yes" : "No") << '\n';
}
// https://nononmath.hatenablog.com/entry/2024/06/11/193707
template <typename mint>
mint bounded_increasing_sequence(const vector<int> &A) {
    const int n = A.size();
    const int m = A[n - 1];
    // 階乗とその逆元の前計算
    vector<mint> fac(n + m + 1), finv(n + m + 1);
    {
        fac[0] = 1;
        for (int i = 1; i <= n + m; i++) fac[i] = i * fac[i - 1];
        finv[n + m] = fac[n + m].inv();
        for (int i = n + m; i >= 1; i--) finv[i - 1] = i * finv[i];
    }
    auto rec = [&](const auto &rec, int l, int r, int d, const vector<mint> &bottom_edge) -> vector<mint> {
        if (l + 1 == r) {
            return vector<mint>(A[l] - d, l == 0 ? mint::raw(1) : bottom_edge[0]);
        }
        int m = (l + r) / 2;
        int h = A[m] - d, w = r - m;
        // 左下の計算
        auto left_edge = rec(rec, l, m, d, vector<mint>(bottom_edge.begin(), bottom_edge.begin() + m - l));
        left_edge.resize(h);
        vector<mint> top_edge(w);
        // 左から上への寄与
        if (h) {
            vector<mint> f(h), g(h + w);
            for (int i = 0; i < h; i++) f[i] = left_edge[i] * finv[h - 1 - i];
            for (int i = 0; i < h + w; i++) g[i] = fac[i];
            f = convolution(f, g);
            for (int i = 0; i < w; i++) top_edge[i] += finv[i] * f[h - 1 + i];
        }
        // 下から上への寄与
        if (h) {
            vector<mint> f(w), g(w);
            for (int i = 0; i < w; i++) f[i] = bottom_edge[i + m - l];
            for (int i = 0; i < w; i++) g[i] = fac[h - 1 + i] * finv[i];
            f = convolution(f, g);
            for (int i = 0; i < w; i++) top_edge[i] += finv[h - 1] * f[i];
        } else {
            for (int i = 0; i < w; i++) top_edge[i] = bottom_edge[i + m - l];
        }
        vector<mint> right_edge(A[r - 1] - d);
        // 左から右への寄与
        if (h) {
            vector<mint> f(h), g(h + w);
            for (int i = 0; i < h; i++) f[i] = left_edge[i];
            for (int i = 0; i < h + w; i++) g[i] = fac[w - 1 + i] * finv[i];
            f = convolution(f, g);
            for (int i = 0; i < h; i++) right_edge[i] += finv[w - 1] * f[i];
        }
        // 下から右への寄与
        if (h) {
            vector<mint> f(w), g(h + w);
            for (int i = 0; i < w; i++) f[i] = bottom_edge[m - l + i] * finv[w - 1 - i];
            for (int i = 0; i < h + w; i++) g[i] = fac[i];
            f = convolution(f, g);
            for (int i = 0; i < h; i++) right_edge[i] += finv[i] * f[w - 1 + i];
        }
        vector<mint> upper_right = rec(rec, m, r, A[m], top_edge);
        int k = upper_right.size();
        // 右側の情報のマージ
        for (int i = 0; i < k; i++) right_edge[i + h] += upper_right[i];
        return right_edge;
    };
    vector<mint> right_edge = rec(rec, 0, n, 0, vector<mint>(n));
    mint res = 0;
    for (mint x : right_edge) res += x;
    return res;
}
string s;
int main(){
    cin >> s;
    int n = s.size(),k = 0;
    vector<int> a;
    for(int i = 0; i < n; i++){
        if(s[i] == 'A') a.eb(i + 1), k++;
    }
    for(int i = 0; i < k; i++){
        a[i] -= i;
    }
    // 0\le B_i < A_i, B_i \le B_{i+1} を数える
    cout << bounded_increasing_sequence<mint>(a).val() << endl;
}