MOD = 998244353
s = read_line.chars
pow2 = [1i64]
s.size.times do
  pow2 << pow2[-1] * 2 % MOD
end
ans = 0i64
add = 1i64
s.each do |ch|
  if ch == 'M'
    add = (add * 3) % MOD
  else
    ans += add
  end
end
puts ans % MOD