Main.cc:19:19: warning: multi-character character constant [-Wmultichar]
cout<<'no'<::length, std::allocator >' from type 'std::__cxx11::basic_string::size_type (std::__cxx11::basic_string::)() const noexcept {aka long unsigned int (std::__cxx11::basic_string::)() const noexcept}' to type 'int'
int a1=a.length;
^