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) 