
You are given an array trees where trees[i] = [x _i , y _i ] represents the location of a tree in the garden.
Fence the entire garden using the minimum length of rope, as it is expensive. The garden is well-fenced only if all the trees are enclosed .
Return the coordinates of trees that are exactly located on the fence perimeter . You may return the answer in any order .
1 <= trees.length <= 3000trees[i].length == 20 <= x _i , y _i <= 100All the given positions are unique .