K-important Strings
Set Difference
And Or Union
Codeforces Round #703 (Div. 2) C1. Guessing the Greatest (easy version)
Codeforces Round #708 (Div. 2) C2. k-LCM (hard version)
CodeCraft-21 and Codeforces Round #711 (Div. 2) C. Planar Reflections
Codeforces Round #712 (Div. 1) A. Balance the Bits
Educational Codeforces Round 107 (Rated for Div. 2) D. Min Cost String
Subarray with given XOR
Maximum Area of Triangle!