program with the following characteristics

1. There is a fruitful function with at least one parameter that does the calculation. Be sure to document your function's behavior and explain the parameters. This function should only return a numeric value. 
2. There is a main function that prompts the user to enter one or more values, calls the function from step 1 with those values, and prints nicely formatted output including those input values along with the value returned by your function.
3. The main function checks the value of the user's input and sets a Boolean variable with the result. Then it prints either the correct result or an error message based on this variable's value.