help needed in a problem

Revision en1, by RedBtats, 2019-08-22 00:36:45

hello

i was trying to solve this problem on a2oj https://a2oj.com/p?ID=292 and it keeps giving me wrong answer and i don't know where is the mistake in my equations so any help is appreciated

my sol : https://ideone.com/DWHlAD

Tags #combinatorics, #math

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en1 English RedBtats 2019-08-22 00:36:45 257 Initial revision (published)