Compilare: user.cpp: In function ‘void op1()’: user.cpp:13:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ( "%d", &X ) ; ^ user.cpp: In function ‘void op2()’: user.cpp:19:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ( "%d", &X ) ; ^ user.cpp: In function ‘int main()’: user.cpp:28:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ( FIN, "r", stdin ) ; ^ user.cpp:29:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ( FOU, "w", stdout ) ; ^ user.cpp:31:30: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] for ( scanf ( "%d", &N ) ; N ; --N ) { ^ user.cpp:32:29: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ( "%d", &se ) ; ^