Compilare: user.cpp: In function ‘int main()’: user.cpp:30:15: warning: variable ‘st’ set but not used [-Wunused-but-set-variable] double dr,st; ^ user.cpp:27:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] { freopen("rays.in", "r",stdin); ^ user.cpp:28:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("rays.out", "w",stdout); ^ user.cpp:31:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &n); ^ user.cpp:35:38: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d%d", &x, &y1, &y2); ^