Compilare: user.cpp: In function ‘void read()’: user.cpp:22:41: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ( "fmcm.in" , "r" , stdin ) ; ^ user.cpp:23:49: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ( "%d %d %d %d" , &N , &M , &S , &D ) ; ^ user.cpp:27:63: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ( "%d %d %d %d" , &x , &y , &capacity , &cost ) ; ^