#include <bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
int main () {
	string s;
	cin >> s;
	int N = s.size();
	std::vector<mint> pw(N);
	pw[0] = 1;
	for (int i = 1; i < N; i ++) {
		pw[i] = pw[i-1] + ((mint)2).pow(i);
	}
	mint ans = 0;
	int c = 0;
	for (auto& a : s) {
		if (a == 'M') {
			c ++;
		} else {
			ans += pw[c];
			c = 0;
		}
	}
	cout << ans.val() << endl;
}