Help needed to understand problem 559C

Правка en1, от akash_goel, 2015-07-24 20:24:01

Here is the link — http://mirror.codeforces.com/problemset/problem/559/C This is similar to this — https://www.codechef.com/CDCRF15R/problems/CWAYS/

In the solutions, I can see inverse factorial being calculated as 

inv(n) = pow(n,mod-2)

I don't get where the mod-2 value comes from. Can someone please explain?

Теги combinatorics, dp

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en1 Английский akash_goel 2015-07-24 20:24:01 378 Initial revision (published)