Compilare: user.cpp: In function ‘int main()’: user.cpp:6: warning: unused variable ‘a’ user.cpp:6: warning: unused variable ‘b’ user.cpp:6: warning: unused variable ‘y’ user.cpp:6: warning: unused variable ‘i’ user.cpp:7: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:8: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result