Codeforces Round 137 (Div. 2) D. Olympiad
Codeforces Round 138 (Div. 1) B. Two Strings
Codeforces Round 138 (Div. 1) C. Partial Sums
Codeforces Round 140 (Div. 1) B. Naughty Stone Piles
Maximum work
Subtree swap
Minimizing graphs’ weights
Sequential tuples
Factors
Codeforces Round 141 (Div. 2) E. The Road to Berland is Paved With Good Intentions