Compilare: main.cpp: In function 'bool query(std::__cxx11::string&)': main.cpp:10:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] int x; cin >> x; return (x == S.size()); ~~^~~~~~~~~~~ main.cpp: In function 'std::__cxx11::string solve(int, int)': main.cpp:20:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(ok && S.size() < N) ~~~~~~~~~^~~