Compilare: user.cpp: In function ‘int main()’: user.cpp:28:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(v.size() > N) ^ user.cpp:44:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(v.size() > N) ^ user.cpp:14:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("undo2.in", "r", stdin); ^ user.cpp:15:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("undo2.out", "w", stdout); ^ user.cpp:19:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &T); ^ user.cpp:23:31: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &op, &x); ^