Compilare: user.cpp: In function 'bool check(std::string, int, char)': user.cpp:21: warning: comparison between signed and unsigned integer expressions user.cpp: In function 'll doit(int, std::string)': user.cpp:28: warning: comparison between signed and unsigned integer expressions user.cpp:28: warning: comparison between signed and unsigned integer expressions user.cpp:31: warning: comparison between signed and unsigned integer expressions