Challenge: Compute Factorial of a Number

Problem statement

Write a function that returns the factorial (!) of any n number. The factorial $n!$ of a number $n$ is defined as:

$n! = n * (n – 1)! , where 0!=1 and 1!=1$

For example: $5! = 5*4*3*2*1= 120$

Input

A number of type uint64, n

Output

A number of type uint64 (because the number increases drastically due to multiplication)

Results will be correct until only 21!. After that, the overflow-error will occur.

Remark: When using type int the calculation is only correct up until 12!. This is, of course, because an int can only contain integers that fit in 32 bits. And, Go doesn’t usually warn against this overflow-error!

Sample input

10

Sample output

3628800

Try to implement the function below. Feel free to view the solution, after giving some shots. Good Luck!