Compilare: user.cpp: In function ‘void input()’: user.cpp:111:32: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ( "%d%d" , &n , &m ) ; ^ user.cpp:115:36: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ( "%d%d" , &x , &y ) ; ^ user.cpp:120:66: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ( "%d%d%d" , &a[ i ].x , &a[ i ].y , &a[ i ].val ) ; ^ user.cpp: In function ‘int main()’: user.cpp:177:42: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ( "metro.in" , "r" , stdin ) ; ^ user.cpp:178:44: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ( "metro.out" , "w" , stdout ) ; ^