Consider the given expression BNF:.

Using recursive descent, and only recursive descent, scan expressions that adhere to this BNF to build their expression tree; write an integer valued function that scans the tree to evaluate the expression represented by the tree.

Input:

A numeric expression adhering to this BNF.

Output:

Some representation of the expression tree.

The result of evaluating the expression.

::= + | - | ::= * | / | - | ( ) ::= 1 | 2 | 3 | 4 | 5 I 6 | 7 | 8 | 9 erin> ::- 011121314151617