@fasterthanlime you are almost there! A hint: you were already thinking in terms of “valve opened” instead of “minutes”, which is great. What the final result could look like is 2 sequences of valve opened. It doesn’t really matter how those sequences align in regards to each other, which is the trap of part 2: all that matters is for the human and the elephant to tell how much pressure they can release if they go visit a sequence of different valves, aka not one already visited and not one visited by the other one at step N.