Compilare: user.cpp: In function ‘void back(int)’: user.cpp:32: warning: unused variable ‘j’ user.cpp: In function ‘int main()’: user.cpp:51: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:52: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:56: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result user.cpp:60: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result