Compilare: user.cpp: In function ‘int64_t check_prefize(size_t, int64_t, const string&)’: user.cpp:12:43: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int idx = prefixsize; idx < B.size(); ++idx) ^ user.cpp: In function ‘uint64_t sumuntil(int64_t)’: user.cpp:62:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (pow2 <= n) ^ user.cpp: In function ‘int main()’: user.cpp:90:42: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (auto numbits = 1; numbits < B.size() && !done; ++numbits) ^