Compilare: main.cpp: In function 'int main()': main.cpp:60:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 60 | while (k < s.length()) | ~~^~~~~~~~~~~~ main.cpp:71:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 71 | while (k < s.length() && s[k] != 'x' && s[k] != '+' && s[k] != '-') | ~~^~~~~~~~~~~~