Compilare: user.cpp: In function ‘void convex_hull(std::vector<point, std::allocator<point> >&)’: user.cpp:64: warning: comparison between signed and unsigned integer expressions user.cpp:104: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘int main()’: user.cpp:153: warning: comparison between signed and unsigned integer expressions user.cpp:162: warning: comparison between signed and unsigned integer expressions user.cpp:182: warning: comparison between signed and unsigned integer expressions user.cpp:195: warning: comparison between signed and unsigned integer expressions user.cpp:198: warning: comparison between signed and unsigned integer expressions user.cpp:215: warning: comparison between signed and unsigned integer expressions user.cpp:113: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:114: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:116: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result user.cpp:119: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result