Compilare: main.cpp: In function 'std::__cxx11::string solve()': main.cpp:7:6: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(i>=s.size()) return ""; ~^~~~~~~~~~ main.cpp:9:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(isalpha(s[i])&&i<s.size()) ~^~~~~~~~~ main.cpp:13:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(isdigit(s[i])&&i<s.size()) ~^~~~~~~~~