Calculating the sum of the integers

Write a program to calculate the sum of the integers between \(N\) and \(M\), where \(N\) and \(M\) are values entered by the user. result = \(\sum_{n = N}^{M} n\)

>>> %Run 
    Enter a number: 0
    Enter a number: 3
    The sum from 0 to 3 is:  6
>>> %Run 
    Enter a number: -5
    Enter a number: 3
    The sum from -5 to 3 is: -9
>>> %Run 
    Enter a number: -8
    Enter a number: 8
    The sum from -8 to 8 is:  0
>>> %Run 
    Enter a number: 4
    Enter a number: 4
    The sum from 4 to 4 is:  4

Insist that the students test their programs by giving them example
test executions.