Compilare: main.cpp: In function 'int main()': main.cpp:27:14: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 27 | while(poz<a.size()) | ~~~^~~~~~~~~ main.cpp:25:9: warning: unused variable 'valid' [-Wunused-variable] 25 | int valid=1; | ^~~~~