HELP IN CODEFORCES ROUND 745 div 2

Revision en1, by Noob5644, 2021-09-30 19:33:43

https://mirror.codeforces.com/contest/1581/problem/A

what is the logic ?? i just know the ans is (2*n)!/2 ,but how ?

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en1 English Noob5644 2021-09-30 19:33:43 148 Initial revision (published)