Problem: Create a program that uses a function to calculate the factorial of a positive whole

number and a function to validate user$$s input. Your program should contain two programmer$-$

built functions in addition to main. No selection structures should be used in this program.

Do not use the same identifier in more than one function.

Your main function should prompt the user to enter a whole number less than or equal to $20.$

Call a function to verify that the entered number is less than or equal to twenty, call the function

to calculate the factorial, return the factorial to main and then output the factorial of the entered

number. Next the main function should output the entered number and the resultant factorial.

Consider carefully what integer data type you should use for the resultant factorial.

The function to validate input should accept the user$$s entered value then use a while loop to

prompt the user to re$-$enter if the entered value was less than $1$ or greater than $20.$ The validated

value should be returned to the function call in main.

The function to calculate the factorial should accept the validated entered value, define any

needed local variables that are needed, and then calculate the factorial using a loop. The factorial

should be returned to the function call in main.

Remember that function definitions should be after the main function and your code

should employ function declarations $($prototypes$).$ In addition to the overall introductory

comments your program should have comments immediately before each function stating

the purpose of that function, input to the function $($what parameters are passed to it$),$

output from the function $($values returned or sent back to the function call plus any output

of values within the function$),$ and processing that occurs within the function.

Take the time to confirm your submissions.