A list is a sequence of or more elements, expressed in this form: [a 1 , a 2 , a 3 , ... , a n ], where each a i is or more consecutive digits or lowercase letters. i.e. each list begins with a left square bracket, then zero or more elements separated by a single comma, followed by a right square bracket. There will be no whitespace characters (spaces, TABs etc) within a list.
In this problem, we use two list operations: append (++) and remove (--).
1. A ++ B: append elements in B to the end of A.
2. A -- B: remove all the elements in B, from A. If something appears more than once in B, remove it that many times in A. If there are many equal elements in A to choose from, remove them from left to right (until all occurrences are removed, or there is no need to remove more elements).
Your task is to write a calculator, evaluating simple expressions or the form "list1 ++ list2" or "list1 -- list2".
There will be at most 10 expressions, one in each line, each having the form "list1 ++ list2" or "list1 -- list2", with no more than 80 characters in total (not counting the newline character). There will be exactly two spaces in each line: one before and one after the operator. Input ends with a single dot. The input is guaranteed to satisfy the restrictions stated above.
For each expression, print its result on a single line.