Always bored with cud-chewing, the cows have invented a new game.
One cow retrieves a set of N
(3 ≤ N
≤ 20) hay bales from the shed
each of which is one unit high. Each bale also has some unique width
and unique breadth.
A second cow tries to choose a set of bales to make the tallest
stack of bales in which each bale can be placed only on a bale whose
own width and breadth are smaller than the width and breadth of the
bale below. Bales can not be rotated to interchange the width and
Help the cows determine the highest achievable tower that can be
legally built form a set of bales.
* Line 1: A single integer, N
* Lines 2..N
+ 1: Each line describes a bale with two space-separated
integers,respectively the width and breadth
* Line 1: The height of the tallest possible tower that can legally be
built from the bales.
Six bales of various widths and breadths
These bales can be stacked for a total height of 5:
[another stacking exists, too]