#include <bits/stdc++.h>
using namespace std;
const int dx[] = {1, 0, -1, 0}, dy[] = {0, -1, 0, 1};
const int dx_8[] = {1, 1, 0, -1, -1, -1, 0, 1},
          dy_8[] = {0, -1, -1, -1, 0, 1, 1, 1};
template <typename T>
inline T GCD(T a, T b) {
  T c;
  while (b != 0) {
    c = a % b;
    a = b;
    b = c;
  }
  return a;
}
template <typename T>
inline T LCM(T a, T b) {
  T c = GCD(a, b);
  a /= c;
  return a * b;
}
template <typename T>
inline T nCr(T a, T b) {
  T i, r = 1;
  for (i = 1; i <= b; i++) {
    r *= (a + 1 - i);
    r /= i;
  }
  return r;
}
template <typename T>
inline T nHr(T a, T b) {
  return nCr(a + b - 1, b);
}
template <typename T>
inline T POW(T a, T b) {
  int i, r = 1;
  for (i = 1; i <= b; i++) {
    r *= a;
  }
  return r;
}
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  string x;
  cin >> x;
  stack<char> sta;
  for (int i = 0; i < (x.size()); ++i) {
    if (x[i] == 'S')
      sta.push(x[i]);
    else {
      if (sta.top() == 'T' or sta.empty())
        sta.push(x[i]);
      else
        sta.pop();
    }
  }
  cout << sta.size() << "\n";
  return 0;
}
