We were waiting several weeks to setting this contest and hope the problem was good enough.
Events
There was a difficulty with 805E - Раскраска мороженого/804C - Раскраска мороженого. A little bug in the checker fortunately yields accepting an incorrect solution of only one person during the contest. I should apologize all of you because of this.
For this sentence, Vertices which have the i-th (1 ≤ i ≤ m) type of ice cream form a connected subgraph.
You can find the meaning of "connected subgraph" with connected and subgraph, thus it can be empty as it is more logical. How ever, I should apologize all of the participants because of weak sample tests in the statement.
I will write the full editorial in the few next days, now some hints and short solutions exist here.
Hints
805C - Найти Амира / 804A - Найти Амира
805D - Минимальное число шагов / 804B - Минимальное число шагов
805E - Раскраска мороженого / 804C - Раскраска мороженого
805F - Матожидание диаметра дерева / 804D - Матожидание диаметра дерева
Solutions
To DO...
To DO...
To DO...
To DO...