What is the logic of marbles in medium practice section…how it can be (n-1)C(k-1)??..pls help…thanks
There are many duplicates questions related to question please see this post .
http://discuss.codechef.com/questions/38041/medium-level-problem-marbles-sigsegv-error.
Hope this will help.
Thanks .
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Just two days back even i was wondering the same… when i found this
and please go through Wikipedia. It contains detailed explanation.
It’ll surely help…!!! 
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Reali thanks…this qstion was disturbing me for two days…
You can use the popular Beggar’s method (is usually taught in High Schools).
Distribution of n-k coins to k beggars.
For distribution of r identical coins among n beggars is c(n+r-1,r-1)
Applying the formula you get required the formula