Convex hull#857
points are given on the plane with their Cartesian coordinates. Find the polygon with minimum perimeter that contains all these points. It is known that the desired polygon has non-zero area.
The first line contains the number of points (3 \le n \le 1000) on the plane. The next lines give the coordinates x_i, y_i (-10000 \le x_i, y_i \le 10000) of these points. All input numbers are integers, all points are distinct.
Print the perimeter of the polygon with one digit after the decimal point.
Example 1