#include <bits/stdc++.h>
using ll = long long;
constexpr int INF = 1073741823;
constexpr int MINF = -1073741823;
constexpr ll LINF = ll(4661686018427387903);
constexpr ll MOD = 1000000007;
const long double PI = acos(-1.0L);
using namespace std;
void scans(string& str) {
  char c;
  str = "";
  scanf("%c", &c);
  if (c == '\n') scanf("%c", &c);
  while (c != '\n' && c != -1) {
    str += c;
    scanf("%c", &c);
  }
}
void scanc(char& str) {
  char c;
  scanf("%c", &c);
  if (c == -1) return;
  while (c == '\n') {
    scanf("%c", &c);
  }
  str = c;
}
double acot(double x) { return PI / 2 - atan(x); }
ll gcd(ll a, ll b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
ll lcm(ll number1, ll number2) {
  return number1 / gcd(number1, number2) * number2;
}
ll LSB(ll n) { return (n & (-n)); }
int main() {
  string s;
  scans(s);
  int cntt = 0, cnts = 0, ans = 0;
  for (int i = 0; i < (s.length()); ++i) {
    if (s[i] == 'T') {
      if (cnts) {
        ans += 2;
        --cnts;
        --cntt;
      }
    } else {
      if (cntt) cnts = cntt = 0;
      ++cnts;
    }
  }
  printf("%d\n", s.length() - ans);
  return 0;
}
