This challenge is about factorial operation.
This is then your number starting multiply it self from one to it self. like:
5! = 1*2*3*4*5 = 120
6! = 1*2*3*4*5*6 = 720
Write a calculator or something like i did in other languages.
from math import factorial
Or written out for clarity, a recursive function:
Remember that 0! = 1 and negative factorial is undefined. Many of the other programs return these two conditions incorrectly.