Test task for creating a dequeue and a calculator.
Accepts a string with data and performs calculations according to the rules of Reverse Polish notation.
input >>> 4 13 5 / +- 13 // 5 + 4
output >>> 6
What is Reverse Polish notation: https://en.wikipedia.org/wiki/Reverse_Polish_notation
Bidirectional queue, with the ability to add and remove items at the beginning and end of the queue.