#include <bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
using mint = atcoder::modint998244353;
// using mint = double;

#define rep(i, l, r) for (int i = (int)(l); i<(int)(r); i++)
#define ll long long
#define ld long double
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define siz(x) (int)(x).size()

template<class T> bool chmin(T& a, T b) { if (a > b) {a = b; return true;} return false; }
template<class T> bool chmax(T& a, T b) { if (a < b) {a = b; return true;} return false; }

const int inf = 1e9;
const ll INF = 4e18;

template<class T> using pq = priority_queue<T, vector<T>, less<T>>;
template<class T> using spq = priority_queue<T, vector<T>, greater<T>>;

vector<int> di = {0, 0, 1, -1};
vector<int> dj = {1, -1, 0, 0};

struct Edge {
    int to, cost;
};

//窃盗元：https://nononmath.hatenablog.com/entry/2024/06/11/193707

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;
}

int main() {
    string S; cin >> S;
    //各iで+iすることにする
    int N = siz(S);
    vector<int> P;
    rep(i, 0, N) {
        if (S[i] == 'A') P.push_back(i); 
    }
    int M = siz(P);
    if (M == 0) {
        cout << 1 << endl;
        return 0;
    }
    vector<int> A(M), B(M);
    //0 <= x[i] + i <= P[i]
    //0 <= x[i] <= P[i] - i
    rep(i, 0, M) {
        A[i] = P[i] - i + 1;
    }
    mint ans = bounded_increasing_sequence(A);

    cout << ans.val() << endl;
}