Compilare: main.cpp: In function 'ull _hash(std::__cxx11::string&)': main.cpp:21:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < s.length (); i++) { ~~^~~~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:35:34: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen ("sabin.in", "r", stdin); ^ main.cpp:36:36: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen ("sabin.out", "w", stdout); ^