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


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

    string S;
    cin >> S;
    mint p = 1;
    mint ans = 0;
    for (char c : S) {
        if (c == 'M') p *= 3;
        else ans += p;
    }
    cout << ans.val() << "\n";
}