/in/p1.cpp: In function 'point Find_P0(std::vector<point>)':
/in/p1.cpp:24:23: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
     for (int i = 0; i < X.size(); i++)
                     ~~^~~~~~~~~~
/in/p1.cpp:33:23: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
     for (int j = 0; j < X.size(); j++)
                     ~~^~~~~~~~~~
/in/p1.cpp: In function 'std::vector<point> Grahams_scan(std::vector<point>)':
/in/p1.cpp:73:14: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
     while (i < X.size()-1)
            ~~^~~~~~~~~~~~
/in/p1.cpp:82:23: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
     for (int j = 0; j < X.size(); j++)
                     ~~^~~~~~~~~~
cc1plus: all warnings being treated as errors