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Difficulty Level: Medium

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Convex Hull
       

Convex Hull of a set of points, in 2D plane, is a convex polygon with minimum area such that each point lies either on the boundary of polygon or inside it. Now given a set of points the task is to find the convex hull of points.

Input:
The first line of input contains an integer T denoting the no of test cases. Then T test cases follow. Each test case contains an integer N denoting the no of points. Then in the next line are N*2 space separated values denoting the points ie x and y.

Output:
For each test case in a new line print the points x and y of the convex hull separated by a space in sorted order where every pair is separated from the other by a ','. If no convex hull is possible print -1.

Constraints:
1<=T<=100
1<=N<=100
1<=x,y<=1000

Example:
Input:

2
3
1 2 3 1 5 6
3
1 2 4 4 5 1

Output:
1 2, 3 1, 5 6
1 2, 4 4, 5 1

** For More Input/Output Examples Use 'Expected Output' option **

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