Write the c++ implementation of following three member functions of the Stack class: getLength(): returns the number of elements in the stack
isEmpty(): returns true if the stack is empty, false otherwise
peek(): returns the value at the top of the stack without removing it. Assumes stack is not empty (no need to check)
The push function is given.

Write code in main to test these functions. Write a loop to enter an unknown number of positive integers. The loop stops when you enter 0 or a negative number. As you are entering integers, they are to be pushed onto a stack. Once done, display the number of elements on the first line and the value at the top of the stack on the next line.

Ex.: If the user enters '10 20 30 -1` the output should be:
3
30

Ex.: If the user enters '-1` the output should be:

0