Your first recursive function

Compute the factorial of N (written N!).

Factorial is defined as:

• 0! = 1 (base case)
• N! = N × (N-1)! (recursive case)

Input:  5
Output: 120

Solve it recursively — the function should call itself.

Constraints

• Use recursion, not a loop.
• N will always be >= 0.