[Codeforces] Round 1009(Div.3) Review(A~D)

https://codeforces.com/contest/2074 I solved 3 problems(A, B, C), and upsolved 1 problem(D). I struggled with problem C during the contest.. When I was accepted in C, I only had 8 minutes, which is insufficient for me to come up with a proper idea fo...