January Challenge 2015
Sereja and Votes, Gcd Queries, Chef and Stones
February Challenge 2015
Chef and Chain, Chef and Equality
March Challenge 2016
Palindromic substrings, maximize the sum
April Challenge 2016
Chef And Coloring, Chef And Magical Path, Chef and Ballons
September Challenge 2016
Chef and digits of a number, Faded Palindromes
March Challenge 2017
Xenny and Alternating Tasks, Bear and Extra Number
November Challenge 2017
Chef goes Left Right Left, Periodic Palindrome Construction, Villages and Tribes
December Challenge 2017
Chef And his Cake, Penalty Shoot-out
Serbia