Compilare: user.cpp: In function ‘void back(int)’: user.cpp:40:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0; i<vb.size(); i++) ^ user.cpp:20:14: warning: unused variable ‘ok’ [-Wunused-variable] bool ok = 0; ^ user.cpp: In function ‘int main()’: user.cpp:73:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i<ans.size(); i++) ^ user.cpp:63:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("bilete.in", "r", stdin); ^ user.cpp:64:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("bilete.out", "w", stdout); ^