input: Write a function to check if a string contains matching parentheses. If the parentheses are matched correctly, return True; otherwise, return False.
  assert matching_paren("()")==True
  assert matching_paren("((")==False
  assert matching_paren(")(")==False
  assert matching_paren("(()")==False
  assert matching_paren("(())")==True
output: def matching_paren(s):
      count = 0
      for char in s:
          if char == '(':
              count += 1
          elif char == ')':
              count -= 1
          if count < 0:
              return False
      return count == 0