#include <bits/stdc++.h>
char x[1 << 19];
int solve(void) {
  std::stack<char> st;
  int len = strlen(x);
  for (int i = 0; i < len; i++) {
    if (x[i] == 'S')
      st.push(x[i]);
    else if (x[i] == 'T' && (st.empty() || st.top() == 'T'))
      st.push(x[i]);
    else
      st.pop();
  }
  return st.size();
}
int main(void) {
  fgets(x, 1 << 19, stdin);
  printf("%d", solve());
  return 0;
}
