Compilare: user.cpp: In function ‘void convex_hull()’: user.cpp:125:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 1; i < p3.size(); ++i) ^ user.cpp:133:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < p3.size(); ++i) { ^ user.cpp: In function ‘void input(int&, std::pair<double, double>*)’: user.cpp:18:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &np); ^ user.cpp:20:52: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%lf %lf", &p[i].first, &p[i].second); ^ user.cpp: In function ‘int main()’: user.cpp:159:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("arie.in", "r", stdin); ^ user.cpp:160:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("arie.out", "w", stdout); ^