#include <bits/stdc++.h>

using namespace std;
int main(){
  string s;
   cin >> s;
  
  s+='S';
  
  int res=s.length()-1;
  int cnt_s=0,cnt_t=0;
  
  if(s[0]=='S') cnt_s++;
  else cnt_t++;
  
  
  
  for(int i=1;i<s.length();i++){
   if(s[i]=='S') { if(s[i-1]=='T') {res-=2*min(cnt_s,cnt_t); 
     cnt_s=cnt_t=0;
                                   }
     cnt_s++;}          
   else {cnt_t++;  
        }
  }
   
  
  
 cout << res << endl;
}_