Compilare: user.cpp: In function ‘std::vector<std::pair<double, double> > hull(std::vector<std::pair<double, double> >&)’: user.cpp:38:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < a.size(); ++i) { ^ user.cpp: In function ‘int main()’: user.cpp:48:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("infasuratoare.in","r",stdin); ^ user.cpp:49:42: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("infasuratoare.out","w",stdout); ^ user.cpp:50:17: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d",&N); ^ user.cpp:53:40: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%lf%lf\n",&v[i].fs,&v[i].sc); ^