Compilare: main.cpp: In function 'int main()': main.cpp:32:24: 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.length(); i++) | ~^~~~~~~~~~~ main.cpp:49:24: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 49 | for (int i=0; i<a.length(); i++) | ~^~~~~~~~~~~