1 
P1  DNA Laboratory 
SPOJ 

2 
P2  Kindergarten 
Codeforces 
Codeforces Round #276 (Div. 1) 
3 
P3  Flea travel 
Codeforces 
Codeforces Beta Round #51 
4 
P4  Prime Number 
Codeforces 
Codeforces Round #209 (Div. 2) 
5 
P5  Bracket Sequence 
Codeforces 
Codeforces Round #138 (Div. 1) & Codeforces Round #138 (Div. 2) 
6 
P6  Appleman and a Sheet of Paper 
Codeforces 
Codeforces Round #263 (Div. 1) & Codeforces Round #263 (Div. 2) 
7 
P7  Great Wall of China 
UVA 

8 
P8  Anton and School  2 
Codeforces 
Codeforces Round #404 (Div. 2) 
9 
P9  Greg and Graph 
Codeforces 
Codeforces Round #179 (Div. 1) & Codeforces Round #179 (Div. 2) 
10 
P10  World Eater Brothers 
Codeforces 
Codeforces Round #148 (Div. 1) & Codeforces Round #148 (Div. 2) 
11 
P11  Mr. Bender and Square 
Codeforces 
Codeforces Round #156 (Div. 2) & Codeforces Round #156 (Div. 1) 
12 
P12  Let's Play Osu! 
Codeforces 
Codeforces Round #146 (Div. 1) & Codeforces Round #146 (Div. 2) 
13 
P13  Little Elephant and Furik and Rubik 
Codeforces 
Codeforces Round #129 (Div. 1) & Codeforces Round #129 (Div. 2) 
14 
P14  Game on Tree 
Codeforces 
Codeforces Round #172 (Div. 1) & Codeforces Round #172 (Div. 2) 
15 
P15  Maximum Xor Secondary 
Codeforces 
Codeforces Round #172 (Div. 1) & Codeforces Round #172 (Div. 2) 
16 
P16  Stadium and Games 
Codeforces 
MemSQL start[c]up Round 1 
17 
P17  Fox and Minimal path 
Codeforces 
Codeforces Round #228 (Div. 1) & Codeforces Round #228 (Div. 2) 
18 
P18  Fox and Card Game 
Codeforces 
Codeforces Round #228 (Div. 1) & Codeforces Round #228 (Div. 2) 
19 
P19  Sleepy Game 
Codeforces 
Codeforces Round #467 (Div. 1) & Codeforces Round #467 (Div. 2) 
20 
P20  Game with String 
Codeforces 
Codeforces Round #468 (Div. 1, based on Technocup 2018 Final Round) & Codeforces Round #468 (Div. 2, based on Technocup 2018 Final Round) 
21 
P21  Teodor is not a liar! 
Codeforces 
Codeforces Round #468 (Div. 1, based on Technocup 2018 Final Round) & Codeforces Round #468 (Div. 2, based on Technocup 2018 Final Round) 
22 
P22  Helga Hufflepuff's Cup 
Codeforces 
Manthan, Codefest 17 
23 
P23  Rowena Ravenclaw's Diadem 
Codeforces 
Manthan, Codefest 17 
24 
P24  Salazar Slytherin's Locket 
Codeforces 
Manthan, Codefest 17 
25 
P25  Startup Funding 
Codeforces 
Manthan, Codefest 16 