We, the round authors, are eternally grateful to all the brave who took part in this round. Sadly there were some issues to encounter, but we hope it only made the contest more interesting :)

Author — GreenGrape
Code: 33946912

Author — GreenGrape
Code: 33946939

Author — rek
Code (rek): 33953146
Code (xen): 33946949
Code (GreenGrape): 33947166

Author — GreenGrape
Code (xen): 33946962
Code (GreenGrape, solution 1): 33946974
Code (GreenGrape, solution 2): 33946993

Author — GreenGrape
Code (xen): 33947002
Code (GreenGrape): 33946911

Hello, Codeforces!

Recently I stumbled upon a certain problem. Given n pairwise distinct positive integers (let's say all of them are less than or equal to 10⁹), you're ought to find such smallest possible k that these numbers modulo k will still be pairwise distinct.

I'll be thankful if someone suggests a non-naive solution (i.e. w/o explicitly calculating all the pairwise differences) or provides some ideas to start with.