Compilare: main.cpp: In function 'nod ec(int&, nod)': main.cpp:81:14: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 81 | while (i < s.length() && s[i] != ')') | ~~^~~~~~~~~~~~ main.cpp:94:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 94 | if (i == s.length() || s[i] == ')') | ~~^~~~~~~~~~~~~