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

#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;

using ll = long long;

int main() {
    string S;
    cin >> S;
    mint x = 1, ans = 0;
    for(char c : S) {
        if(c == 'M') x *= 3;
        else ans += x;
    }
    cout << ans.val() << endl;
}