Given N points, find the convex hull
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Each testcase starts with 3<= N <= 10^6, which represents the number of points. Following N lines describe N points x, y-coordinate, where |x|, |y| <= 1000, and x, y are intergers. Input file ends up with a single 0.
There are no such cases that one line can pass through every point.
Each testcase contains two lines.
Frist line prints Case #: , where # is the number of testcases.
Second line output the index of the points in counterclockwise order(index is the order of input, and the first point has index "1"). Start from the leftmost point, or the lowest one in case of a tie.