import sys
X = list(sys.stdin.readline().strip())
N = len(X)

def solve():
    cnt = 0
    i = 0
    while True:
        while i < N and X[i] != 'S':
            i += 1
        j = i + 1
        while j < N and X[j] != 'T':
            j += 1
        if j == N:
            return N - 2*cnt
        cnt += 1
        X[i] = ' '
        X[j] = ' '
        i += 1
        j += 1

print(solve())