|A simple calculator accepts the following kinds of strings as input:
|-||input will contain between 3 and 50 characters inclusive.|
|-||input will have the form <NUM><OP><NUM> where|
<NUM> is a positive integer between 1 and 10000 inclusive, that may contain leading zeros and
<OP> is one of (quotes for clarity) '+','*','-', or '/'.
|-||input will not contain any spaces.|