February Challenge 2015
Time to Study Graphs with Chef, Chef and Strange Formula, Chef and Strings, Let us play with rank list, Xor Matrix, Jigsaw Puzzle Solving, Chef and Equality, Devu and Locks, Chef and Chain
March Challenge 2015
Chef and Notebooks, Counting on a Tree, Matrix, Sign Wave, Devu and his Class, Sereja and Random Array, Chef and Problems, Count Substrings
April Challenge 2015
Chef and Piano Scales, Devus and their voting system, Black-white Board Game, Inversion sorting, Chef and Interview, Chef and Array, Count Sequences, Broken Telephone
February Lunchtime 2015
Lucky Four, Heavy-light Decompositions, The Warehouse
September Challenge 2016
Faded Palindromes, Chef and calculation, Chef and digits of a number, Dividing Machine, Chef and Friends
February Challenge 2017
Eugene and big number, Chef and Triangles, Chef and his Best Friend, Chef and His Apartment Dues
January Challenge 2019 Division 1
Yet Another Problem About Sequences, Different Neighbours, Partition the Graph, Distinct Pairs, A Pizza Slice
China