In computer science arithmetic expressions can be written in three different styles.

1. Infix e.g. (3*6) + (4*7) = 46
2. Prefix e.g. + * 3 6 * 4 7 = 46
3. Postfix e.g. 3 6 * 4 7 * + = 46

Question: Write a program that is going to read a post fix expression and then evaluate and show the result on screen.
Note: Use Stacks to solve the problem.

Input specification
A postfix arithmetic expression will be given ending with an equal operator (=).
The expression may contain only numbers and 5 arithmetic operators: '+', '-', '*', '/', and '='.
The numbers will be preceded by '#'. Operators and operands are separated by spaces.
There are at most 10 consecutive numbers in the given expression.

Output specification
Calculate and show one integer: the result of postfix expression.

Output Explanation :
The expression given in the first sample can be written as:    6 * (7 + (12 / 6)) - 21 = 33