Compilare: main.cpp: In function 'bool chk(const string&, const string&)': main.cpp:14:22: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 14 | for ( int i = 1; i <= a.length(); ++i ) { | ~~^~~~~~~~~~~~~ main.cpp:15:21: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare] 15 | for ( int j = 1; j <= b.length(); ++j ) { | ~~^~~~~~~~~~~~~