The test cases for the problem TKCONVEX are very weak. Even though the problem was rejudged during the contest, still I am able to find many solutions which fail very simple test case.
8 4
1 2 3 6 6 6 6 13
It can be seen that 1 2 6 6 form a convex polygon, and 3 6 6 13 form the second one.
