Compilare: user.cpp: In function ‘bool on_segment(point, point, point)’: user.cpp:21: warning: comparisons like ‘X<=Y<=Z’ do not have their mathematical meaning user.cpp:21: warning: comparisons like ‘X<=Y<=Z’ do not have their mathematical meaning user.cpp: In function ‘int main()’: user.cpp:32: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:36: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result user.cpp:38: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result