Write a program where you solve these problems, use recursive functions.

Using haskel

$1.$ Factorial

Description: Calculates the factorial of a positive integer n$.$

Input: A positive integer n$.$

Output: The factorial of n$.$

$2.$ Fibonacci

Description: Calculates the nth Fibonacci number.

Input: A positive integer n$.$

Output: The nth Fibonacci number.

$3.$ Sum of the digits of a number

Description: Calculates the sum of the digits of a positive integer n$.$

Input: A positive integer n$.$

Output: The sum of the digits of n$.$