Mr. Cai and TT were playing in a beautiful sandy beach, and TT discovered a tree branch with many ant walking on it.
TT noticed that when one ant meet another, they would turn back and keep on walking, when an ant walk straight to the side of the branch and there is no block on it's road(if exist, this ant will meet another and turn back,then it can't walk out the branch), it will walk out the branch and disappear. Mr.Cai also noticed this, he said:"TT, if you tell me how long will all the ants disappear and how long is the first ant walked out, I'll buy you many many snacks as praise."
20 3 3 l 12 r 7 r
max = 13 min = 3