def compute_floor(parens):
  """
  r = len(''.join(parens.split(')')))
  r = r - len(''.join(parens.split('(')))
  return r
  """

  r = 0

  for pos, p in enumerate(parens, start=1):
    if r < 0: return pos - 1

    if p == '(':
      r += 1
    elif p == ')':
      r -= 1

  return None

if __name__ == '__main__':
  with open('./input') as f:
    parens = f.read().strip()

  res = compute_floor(parens)
  print('*** Answer1={}'.format(res))