#include <bits/stdc++.h>
using namespace std;
const int P = 1e9 + 7, INF = 0x3f3f3f3f;
long long gcd(long long a, long long b) { return b ? gcd(b, a % b) : a; }
long long qpow(long long a, long long n) {
  long long r = 1 % P;
  for (a %= P; n; a = a * a % P, n >>= 1)
    if (n & 1) r = r * a % P;
  return r;
}
long long inv(long long first) {
  return first <= 1 ? 1 : inv(P % first) * (P - P / first) % P;
}
inline int rd() {
  int first = 0;
  char p = getchar();
  while (p < '0' || p > '9') p = getchar();
  while (p >= '0' && p <= '9') first = first * 10 + p - '0', p = getchar();
  return first;
}
const int N = 1e6 + 50;
char s[N];
int n;
int main() {
  scanf("%s", s + 1);
  n = strlen(s + 1);
  string v;
  for (int i = 1; i <= n; ++i) {
    if (v.size() && v.back() == 'S' && s[i] == 'T')
      v.pop_back();
    else
      v.push_back(s[i]);
  }
  cout << v.size() << '\n';
}
