Compilare: user.cpp: In function ‘void back(int)’: user.cpp:120: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘int main()’: user.cpp:146: warning: unused variable ‘i’ user.cpp:146: warning: unused variable ‘j’ user.cpp:147: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:148: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result user.cpp:149: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result