Compilare: user.cpp: In function ‘void read()’: user.cpp:12: warning: unused variable ‘i’ user.cpp:15: warning: ignoring return value of ‘char* fgets(char*, int, FILE*)’, declared with attribute warn_unused_result user.cpp: In function ‘void write()’: user.cpp:39: warning: format ‘%lld’ expects type ‘long long int’, but argument 2 has type ‘int’ user.cpp:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result