Compilare: main.cpp: In function 'void buildZ(std::string&)': main.cpp:10:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 10 | for (int i = 1; i < a.length(); i++) { | ~~^~~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:42:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 42 | for (int i = 0; i < a.size(); i++) { | ~~^~~~~~~~~~