🚀 go-pugleaf

The way to do this problem in a brute force way is:

- prime factorize n - not to hard you already have n factors
  so you get something like 2^a * 3^b * 5^c ...

- now cast away the fives by pairing with twos
  so you get something like 2^(a-c) * 3^b * 7^d

- now just multiply all the terms together only remembering 
the last digit each time ( just take it mod 10 after is 
multiply ).



eg.  LASTNONZERODIGITOF(6!)
    = LASTNONZERODIGITOF(2^4 * 3^2 * 5)
    = LASTNONZERODIGITOF(2^3 * 3^2)
    = No Problem can't get messed up by 10's!


- I bet though there is a MUCH faster way of doing this.

- Question for you - what is the running time of the above 
  algorithm? 




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