Compilare: user.cpp: In function ‘void read()’: user.cpp:39:41: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ( "cmcm.in" , "r" , stdin ) ; ^ user.cpp:40:41: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ( "%d %d %d" , &N , &M , &E ) ; ^ user.cpp:45:48: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ( "%d %d %d" , &x , &y , &cost ) ; ^