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

using ll = long long;

bool chmax(auto &a, auto b) { return a < b ? a = b, 1 : 0; }
bool chmin(auto &a, auto b) { return a > b ? a = b, 1 : 0; }

template<ll MOD>
struct modint {
    using M = modint;
    ll x;
    modint() : x(0) {}
    constexpr modint(ll v) : x(v % MOD) {
        if (x < 0) x += MOD;
    }
    ll val() { return x; }
    friend M operator+(M a, M b) { return a.x + b.x; }
    friend M operator-(M a, M b) { return a.x - b.x; }
    friend M operator*(M a, M b) { return a.x * b.x; }
    friend M operator+=(M& a, M b) { return a = a + b; }
    friend M operator*=(M& a, M b) { return a = a * b; }
    M pow(ll k) const {
        M a = x, res = 1;
        while (k > 0) {
            if (k & 1) res *= a;
            a *= a;
            k >>= 1;
        }
        return res;
    }
};

using mint = modint<998244353>;

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);

    string S; cin >> S;
    int N = S.size();
    mint ans = 0;
    vector<mint> dp(N + 1);
    dp[0] = 1;
    for (int i = 0; i < N; ++i) {
        if (S[i] == 'A') {
            ans += dp[i];
            dp[i + 1] = dp[i];
        } else {
            dp[i + 1] = 3 * dp[i];
        }
    }
    cout << ans.val() << '\n';
}