Compilare: main.cpp: In function 'int main()': main.cpp:20:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 20 | for (int i=1; i<a.length(); i++) | ~^~~~~~~~~~~ main.cpp:25:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 25 | for (int i=0; i<a.length(); i++) | ~^~~~~~~~~~~ main.cpp:30:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 30 | for (int i=0; i<a.length(); i++) | ~^~~~~~~~~~~ main.cpp:40:29: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 40 | for (int i=a.length(); i<b.length(); i++) | ~^~~~~~~~~~~