#include <iostream>
#include <numeric>
#include <ranges>
#include <vector>

#include <atcoder/convolution>
#include <atcoder/modint>

using mint = atcoder::modint998244353;

template <class T>
mint count_increasing_sequence_with_upper_bound(
    const std::vector<T>& upper_bounds) {
    const auto n = upper_bounds.size();
    const auto m = upper_bounds.end()[-1];

    std::vector<mint> fact(n + m + 1), fact_inv(n + m + 1);
    {
        fact[0] = 1;

        const auto &range = std::views::iota(1) | std::views::take(n + m);

        for(const auto i : range) {
            fact[i] = i * fact[i - 1];
        }

        fact_inv[n + m] = fact[n + m].inv();

        for(const auto i : range | std::views::reverse) {
            fact_inv[i - 1] = i * fact_inv[i];
        }
    }

    const auto&& rec = [&](auto&& rec, const int l, const int r,
                           const int d, const std::vector<mint>& bottom) {
        if(l + 1 == r) {
            return std::vector(upper_bounds[l] - d,
                               l == 0 ? mint::raw(1) : bottom[0]);
        }

        const int m = (l + r) / 2;
        const int h = upper_bounds[m] - d, w = r - m;

        auto left = rec(rec, l, m, d,
                        std::vector(bottom.begin(), bottom.begin() + m - l));
        left.resize(h);

        std::vector<mint> top(w);

        std::vector<mint> right(upper_bounds[r - 1] - d);

        if(h > 0) {
            {
                std::vector<mint> f(h), g(h + w);

                for(const auto i : std::views::iota(0, h)) {
                    f[i] = left[i] * fact_inv[h - 1 - i];
                }

                for(const auto i : std::views::iota(0, h + w)) {
                    g[i] = fact[i];
                }

                f = convolution(f, g);

                for(const auto i : std::views::iota(0, w)) {
                    top[i] += fact_inv[i] * f[h - 1 + i];
                }
            }
            {
                std::vector<mint> f(w), g(w);

                for(const auto i : std::views::iota(0, w)) {
                    f[i] = bottom[i + m - l];
                }
                for(const auto i : std::views::iota(0, w)) {
                    g[i] = fact[h - 1 + i] * fact_inv[i];
                }

                f = convolution(f, g);

                for(const auto i : std::views::iota(0, w)) {
                    top[i] += fact_inv[h - 1] * f[i];
                }
            }

            {
                std::vector<mint> f(h), g(h + w);

                for(const auto i : std::views::iota(0, h)) {
                    f[i] = left[i];
                }
                for(const auto i : std::views::iota(0, h + w)) {
                    g[i] = fact[w - 1 + i] * fact_inv[i];
                }

                f = convolution(f, g);

                for(const auto i : std::views::iota(0, h)) {
                    right[i] += fact_inv[w - 1] * f[i];
                }
            }
            {

                std::vector<mint> f(w), g(h + w);

                for(const auto i : std::views::iota(0, w)) {
                    f[i] = bottom[m - l + i] * fact_inv[w - 1 - i];
                }
                for(const auto i : std::views::iota(0, h + w)) {
                    g[i] = fact[i];
                }

                f = convolution(f, g);

                for(const auto i : std::views::iota(0, h)) {
                    right[i] += fact_inv[i] * f[w - 1 + i];
                }
            }
        } else {
            for(const auto i : std::views::iota(0, w)) {
                top[i] = bottom[i + m - l];
            }
        }

        std::vector<mint> upper_right = rec(rec, m, r, upper_bounds[m], top);

        const auto k = upper_right.size();

        for(const auto i : std::views::iota(0uz, k)) {
            right[i + h] += upper_right[i];
        }

        return right;
    };

    const auto right = rec(rec, 0, n, 0, std::vector<mint>(n));
    return std::accumulate(right.begin(), right.end(), mint(0));
}

int main() {
    std::string s;
    std::cin >> s;

    std::vector<int> A = {1};

    int val = 1;
    for(const auto &c : s | std::views::reverse) {
        if(c == 'A') {
            ++val;
        } else {
            A.push_back(val);
        }
    }

    std::cout << count_increasing_sequence_with_upper_bound(A).val() << '\n';
}