1 
P1  Herding 
SPOJ 

2 
P2  Two Paths 
Codeforces 
Codeforces Beta Round #14 (Div. 2) 
3 
P3  Caterpillar 
TJU 

4 
P4  Vasya and String 
Codeforces 
Codeforces Round #354 (Div. 2) 
5 
P5  Search in the dictionary! 
SPOJ 

6 
P6  RedGreen Towers 
Codeforces 
Codeforces Round #273 (Div. 2) 
7 
P7  Bear and Friendship Condition 
Codeforces 
VK Cup 2017  Round 1 
8 
P8  Activities 
SPOJ 

9 
P9  Minimum number of steps 
Codeforces 
Codeforces Round #411 (Div. 1) & Codeforces Round #411 (Div. 2) 
10 
P10  Mice problem 
Codeforces 
Tinkoff Challenge  Elimination Round 
11 
P11  Find Amir 
Codeforces 
Codeforces Round #411 (Div. 1) & Codeforces Round #411 (Div. 2) 
12 
P12  Vertex Cover 
SPOJ 

13 
P13  Divide by Three 
Codeforces 
Educational Codeforces Round 18 
14 
P14  Unbearable Controversy of Being 
Codeforces 
Codeforces Round #277.5 (Div. 2) 
15 
P15  Vanya and Scales 
Codeforces 
Codeforces Round #308 (Div. 2) 
16 
P16  Dima and Staircase 
Codeforces 
Codeforces Round #167 (Div. 2) & Codeforces Round #167 (Div. 1) 
17 
P17  Little Girl and Maximum XOR 
Codeforces 
Codeforces Round #169 (Div. 2) 
18 
P18  Watto and Mechanism 
Codeforces 
Codeforces Round #291 (Div. 2) 
19 
P19  Main Sequence 
Codeforces 
Codeforces Round #176 (Div. 1) & Codeforces Round #176 (Div. 2) 