Factorial Function

Write a function factorial that takes an integer as an argument. It returns the factorial of a given number.

Examples

factorial(0) ➞ 1
factorial(4) ➞ 24
factorial(5) ➞ 120

Note 

• Writing a function is compulsory for this problem. Use "factorial" as a function name.
• Don't forget to return the result
• Don't write recursive function