The program reads from standard input an expression written in postfix notation (also known as Reverse Polish Notation or RPN). In this notation, the operator is written after its two operands, and tokens are separated by single spaces.
For example, the infix expression (10 - 2) 3 is written in postfix as 10 2 - 3 .
The program evaluates the expression and prints its value. Supported operators are +, -, *, and / (integer division, as in C++).