According to input data 9!! = 9(9-1*2)(9-2*2)(9mod2) = 9*7*5*1=315

Edited by author 04.06.2015 18:13

Edited by author 04.06.2015 18:13

You forgot the multiplication with 3.
9 !! = 9(9-1*2)(9-2*2)(9-3*2)(9-4*2) = 9 * 7 * 5 * 3 * 1 = 945
The formula presented in the text has some "...", meaning that the product continues until the last member is either n mod k (in case n doesn't divide k) or k (in the other case).

it will minus(-) what your input in string.... like you input (!!!) and enter 9,,,so
there 9-3=6 then 6-3=3 then 3-3=1 so 9*6*3*1=162

so that's why u can solve this by 9 !!==> 9-2=7,7-2=5,5-2=3,3-2=1;
so 9*7*5*3*1=945.

that's it