문제
From her pasture on the farm, Bessie the cow has a wonderful view of a mountain range on the horizon. There are
Bessie is trying to count all of the mountains, but since they all have roughly the same color, she cannot see a mountain if its peak lies on or within the triangular shape of any other mountain.
Please determine the number of distinct peaks, and therefore mountains, that Bessie can see.
Problem credits: Brian Dean
입력
The first line of input contains
출력
Please print the number of mountains that Bessie can distinguish.
예제1
3
4 6
7 2
2 5
2
In this example, Bessie can see the first and last mountain. The second mountain is obscured by the first.