import collections

s=input()
n=len(s)
slen=collections.deque()
tlen=collections.deque()
cnt=0
ans=0
for i in range(n):
  if s[i]=='S':
    tpos=i
    break
else:
  tpos=n
for i in range(n-1,-1,-1):
  if s[i]=='T':
    spos=i
    break
else:
  spos=-1
s=s[tpos:spos+1]+'x'
for i in range(len(s)-1):
  cnt+=1
  if s[i]!=s[i+1]:
    if s[i]=='S':
      slen.append(cnt)
      cnt=0
    else:
      tlen.append(cnt)
      cnt=0
for i in range(len(slen)):
  stmp,ttmp=slen.popleft(),tlen.popleft()
  if stmp>ttmp:
    ans+=ttmp
    tmp=slen.popleft()+(stmp-ttmp)
    slen.appendleft(tmp)
  else:
    ans+=stmp
print(n-ans*2)