#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main()
{
  const int mod = 998244353;
  string s;
  cin >> s;
  long long ans = 0;
  reverse(s.begin(), s.end());
  for (auto c : s)
  {
    if (c == 'M') ans = ans * 3 % mod;
    else ans = (ans + 1) % mod;
  }
  cout << ans << endl;
}