- Time limit: 1.00 s
- Memory limit: 512 MB
Input
The first input line has an integer $n$: the number of points.
After this, there are $n$ lines that describe the points. Each line has two integers $x$ and $y$: the coordinates of a point.
You may assume that each point is distinct, and the area of the hull is positive.
Output
First print an integer $k$: the number of points in the convex hull.
After this, print $k$ lines that describe the points. You can print the points in any order. Print all points that lie on the convex hull.
Constraints
- $3 \le n \le 2 \cdot 10^5$
- $-10^9 \le x, y \le 10^9$
Input:
6
2 1
2 5
3 3
4 3
4 4
6 3
Output:
4
2 1
2 5
4 4
6 3