Reverse Polish Notation Calculator

This problem involves implementing a simplified stack-based calculator which uses Reverse Polish Notation (RPN). In RPN, every operator follows all of its operands. For example, to add 3 and 4, one would write 3 4 + rather than 3 + 4. This eliminates the need for parentheses to define order of operations.

Your task is to implement an RPN calculator that supports the four basic arithmetic operators: addition (+), subtraction (-), multiplication (*) and division (/). Note that division should perform integer division with truncation toward zero. For example, the equation

\(\frac{-7}{3} = -2\)

should evaluate to -2.

inputFormat

The input will be provided as a single line read from stdin. The line contains space-separated tokens. Each token is either an integer or one of the four operators: +, -, *, or /.

For example: 2 1 + 3 *

outputFormat

Output a single integer that is the result of evaluating the RPN expression, printed to stdout.

2 1 + 3 *

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