# include <iostream>
# include <fstream>
# include <cstdio>
# include <cstdlib>
# include <vector>
# include <algorithm>
# include <stack>
using namespace std;
stack<char>ch;
int main () {
	string s;
	int ans = 0;
	int n = 1010000;
	cin>>s;
	int sz = s.size();
	for(int i=s.size();i>=0;i--){
		ch.push(s[i]);
	}
	while(!ch.empty()){
		char t = ch.top();
		ch.pop();
		if(t=='S'){
			char tt = ch.top();
			ch.pop();
			if(tt=='T'){
				ans+=2;
			}
		}
	}
	cout<<sz-ans;
  
	
	return 0;
}