Compilare: user.cpp: In function ‘void backTr(int, std::unordered_set<std::basic_string<char> >&, std::string&)’: user.cpp:22:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (pattern.size() >= n) { ^ user.cpp:39:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (pattern.size() >= n) { ^ user.cpp: In function ‘int main()’: user.cpp:56:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("biti.in", "r", stdin); ^ user.cpp:57:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("biti.out", "w", stdout); ^ user.cpp:60:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &n); ^