Folding My T-Shirt

I have a T-Shirt. When I don’t wear it any more, I fold it up. For most of the time, I can find a line so that the parts of the T-shirt on both sides are symmetrical. Then, I can fold it along that line. But sadly, I cannot find such a line for some strange (really really strange, see sample input ^_^) T-shirts. In the example above, I can fold the T-shirt along the dash line, then, I got the figure on the right. Could you tell me if I can succeed? Input The first line of the input contains a single integer t (t ≤ 20) indicating the number of test cases. Each test case begins with a line containing a single integer n (3 ≤ n ≤ 100) indicating the number of points of the polygon. In the next n lines each contain a pair of integers (xi, yi), indicating the position of the points. The points are given in the counter-clockwise order. The T-Shirt is valid. i.e not self-crossing. But the T-Shirt maybe not convex. Output For each test case, output a line corresponding the answer. Answer ‘Yes’ if the T-Shirt can be folded, ‘No’ otherwise. Sample Input 2 3 00 50 11 8

2/2 10 20 21 -2 1 -2 0 -1 0 -1 -3 1 -3 Sample Output No Yes