Compilare: user.cpp: In function ‘void back()’: user.cpp:64: warning: unused variable ‘k’ user.cpp: In function ‘int main()’: user.cpp:88: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:89: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:91: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result user.cpp:96: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result