1 
P1  Princess Farida 
SPOJ 

2 
P2  Yet Another Problem On a Subsequence 
Codeforces 
Educational Codeforces Round 46 (Rated for Div. 2) 
3 
P3  XOR and OR 
Codeforces 
Codeforces Round #173 (Div. 2) 
4 
P4  Hard problem 
Codeforces 
Codeforces Round #367 (Div. 2) 
5 
P5  Good Sequences 
Codeforces 
Codeforces Round #162 (Div. 1) & Codeforces Round #162 (Div. 2) 
6 
P6  Little Girl and Maximum XOR 
Codeforces 
Codeforces Round #169 (Div. 2) 
7 
P7  Square Difference 
Codeforces 
Lyft Level 5 Challenge 2018  Elimination Round 
8 
P8  Ladder 
Codeforces 
Codeforces Round #171 (Div. 2) 
9 
P9  Plasticine zebra 
Codeforces 
Codeforces Round #505 (rated, Div. 1 + Div. 2, based on VK Cup 2018 Final) 
10 
P10  Countingout Rhyme 
Codeforces 
Educational Codeforces Round 18 
11 
P11  Hills 
Codeforces 
Codeforces Round #500 (Div. 1) [based on EJOI] & Codeforces Round #500 (Div. 2) [based on EJOI] 
12 
P12  Caesar's Legions 
Codeforces 
Codeforces Beta Round #89 (Div. 2) 
13 
P13  Bus Number 
Codeforces 
Codeforces Round #491 (Div. 2) 
14 
P14  Bicolorings 
Codeforces 
Educational Codeforces Round 51 (Rated for Div. 2) 
15 
P15  Flowers 
Codeforces 
Codeforces Round #271 (Div. 2) 
16 
P16  Pictures with Kittens (easy version) 
Codeforces 
Codeforces Round #521 (Div. 3) 
17 
P17  Convert to Ones 
Codeforces 
Codeforces Round #493 (Div. 1) & Codeforces Round #493 (Div. 2) 
18 
P18  LionAge II 
Codeforces 
Codeforces Beta Round #66 
19 
P19  spalindrome 
Codeforces 
Educational Codeforces Round 14 
20 
P20  George and Job 
Codeforces 
Codeforces Round #267 (Div. 2) 
21 
P21  Alternative Thinking 
Codeforces 
Codeforces Round #334 (Div. 1) & Codeforces Round #334 (Div. 2) 
22 
P22  Multijudge Solving 
Codeforces 
Educational Codeforces Round 25 
23 
P23  The Knapsack Problem 
SPOJ 

24 
P24  Barcode 
Codeforces 
Codeforces Round #139 (Div. 2) 
25 
P25  kTree 
Codeforces 
Codeforces Round #247 (Div. 2) 
26 
P26  Monitor 
Codeforces 
Educational Codeforces Round 28 
27 
P27  Minimizing the String 
Codeforces 
Educational Codeforces Round 54 (Rated for Div. 2) 
28 
P28  Buns 
Codeforces 
Codeforces Beta Round #82 (Div. 2) 