Compilare: user.cpp: In function ‘void read()’: user.cpp:17:46: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen( "ciclueuler.in" , "r" , stdin ) ; ^ user.cpp:18:32: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf( "%d %d" , &N , &M ) ; ^ user.cpp:21:36: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf( "%d %d" , &x , &y ) ; ^