Compilare: user.cpp: In function ‘void back(int)’: user.cpp:130: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘int main()’: user.cpp:156: warning: unused variable ‘i’ user.cpp:156: warning: unused variable ‘j’ user.cpp:157: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:158: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:159: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result