1 
P1  Aggressive cows 
SPOJ 

2 
P2  Copying Books 
SPOJ 

3 
P3  They Are Everywhere 
Codeforces 
Codeforces Round #364 (Div. 2) 
4 
P4  Magic Powder  2 
Codeforces 
Codeforces Round #350 (Div. 2) 
5 
P5  Books 
Codeforces 
Codeforces Round #171 (Div. 2) 
6 
P6  Tavas and Karafs 
Codeforces 
Codeforces Round #299 (Div. 2) & Codeforces Round #299 (Div. 1) 
7 
P7  Kefa and Company 
Codeforces 
Codeforces Round #321 (Div. 2) 
8 
P8  Worms 
Codeforces 
Codeforces Round #271 (Div. 2) 