#include <bits/stdc++.h>
using namespace std;
vector<char> v;
char x;
int main() {
  while (scanf("%c", &x)) {
    v.push_back(x);
  }
  int num = 0;
  for (vector<char>::iterator it = v.begin() + 1; it != v.end(); it++) {
    if (*(it - 1) == 'S' && *it == 'T') {
      v.erase(it - 1);
      v.erase(it);
      num++;
      it = v.begin() + 1;
    }
    if (num == 10 ^ 10000) break;
  }
  cout << v.size();
  return 0;
}
