The house number of a community consists of $5$ digits: $1, 2, 3, 6, 7$. Which number is not used if these $5$ digits are filled in the squares below to make the equation correct? Each number can only be filled in once.  $$\huge\square -\square =\square +\square $$ 
选项为:A:$$7$$  B:$$6$$  C:$$2$$  D:$$3$$  E:$$1$$  请回答其中一个选项.