There are

ants living on a stick of length
)
units. The initial position of the

-th ant is

units away from the left side of the stick. Some of the ants are facing left at the beginning, while the others are facing right. All ants will move at a speed of 1 unit per second in the direction they're facing. When two ants meet face to face at the same point, both of them will turn around instantly and move on.
There are also two obstacles on the sides of the stick, one located on the leftmost and the other on the rightmost. When an ant runs into one of them, it will also turn around instantly and move on. However, the obstacles aren't indestructible. The left one will break after

hits, while the right one will break for

hits. After an ant passes through a broken obstacle it will fall from the stick. Note that the number of hits is calculated independently for each obstacle, and that the ant which breaks the obstacle will also turn around and will not fall immediately.
In how many seconds will all ants fall from the stick?