Suppose I have a list:

`l={{1,4},{2,4},{3,5},{4,6},{5,3},{6,2}}`

How can I select the elements of the list in the second element is decreasing and first element of the list increasing? That is, I want `{{1,4},{2,4},{5,3},{6,2}`?

I know there is a simple function in Mathematica to do this. But I cannot find it.