Codeforces Round 157 (Div. 1) B. Little Elephant and Elections
Codeforces Round 160 (Div. 1) B. Maxim and Restaurant
Codeforces Round 171 (Div. 2) E. Beautiful Decomposition
Codeforces Round 175 (Div. 2) D. Permutation Sum
Breaking walls
Handshakes in a party
Velocities of balls
N-dimensional plane
Maximum OR
Croc Champ 2013 - Round 1 D. Connected Components