/in/foo.cc: In function 'int main()':
/in/foo.cc:47:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i = 0; i < convex_hull.size(); i++)
                    ~~^~~~~~~~~~~~~~~~~~~~
/in/foo.cc:49:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         int k = (i==convex_hull.size()-1 ? t : get<0>(convex_hull[i+1]));
                  ~^~~~~~~~~~~~~~~~~~~~~~