Compilare: main.cpp: In function 'void buildZ(std::string&)': main.cpp:11:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 11 | for(int i=1;i<a.length();i++) | ~^~~~~~~~~~~ main.cpp: In function 'int main()': main.cpp:32:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 32 | for(int i=0;i<a.size();i++) | ~^~~~~~~~~