Compilare: user.cpp: In function ‘std::string Query(long long int)’: user.cpp:162:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0; i<Number.length (); ++i) ^ user.cpp: In function ‘int main()’: user.cpp:180:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0; i<Number.length (); printf ("%c", Number[i]), ++i); ^