Compilare: user.cpp: In function ‘int main()’: user.cpp:51:36: warning: format ‘%lu’ expects argument of type ‘long unsigned int’, but argument 2 has type ‘std::vector<std::pair<double, double> >::size_type {aka unsigned int}’ [-Wformat=] printf("%lu\n", convex_hull.size()); ^ user.cpp:37:42: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("infasuratoare.in", "rt", stdin); ^ user.cpp:38:44: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("infasuratoare.out", "wt", stdout); ^ user.cpp:42:17: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &n); ^ user.cpp:46:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%lf%lf", &a, &b); ^