I would like to give some feedback about ...

From: http://www.checkio.org/mission/feed-pigeons/solve/

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It seems that their is some bug with result check in feed-pigeons. No. of pigeons cannot be 2, which is the result of checkio(3) No. of pigeons can only be 1,3,6,10,15, which is the sum of arithmetic progression n(n+1)/2