#include <bits/stdc++.h>
using namespace std;
int main() {
  string w;
  cin >> w;
  int len = w.size();
  for (int i = 1; i < len; ++i) {
    if (w[i - 1] == 'S' && w[i] == 'T') {
      w.erase(w.begin() + i);
      w.erase(w.begin() + i - 1);
      i = i - 2;
      len = len - 2;
    }
  }
  cout << w.size() << endl;
}
