Atcoder Beginner Contest 186: Post-contest Discussion (+ Chess with Viewers)

I explain my solutions to ABC 186, then play some chess with viewers.

0:00 Intro/chatting/waiting to start
7:25 A (Brick)
9:50 B (Blocks on Grid)
13:00 C (Unlucky 7)
17:47 D (Sum of difference)
26:10 E (Throne)
38:05 F (Rook on Grid)
59:25 Chatting
1:11:51 Chess with Viewers!

[wolfie-]

in Atcoder ABC 186 problem E, we want to solve the eqn ->( S + Kx)%N ==0 --> S + Kx = Ny --> Kx - Ny = - S .. How does eqn. Kx - Ny = - S change to Kx + Ny = N - S ?

[hitman]

If possible please explain codeforces technocup div2c and div2d

[amurto]

(S + Kx) % N = 0 and S + Kx congruent to 0 mod N mean the same ?