"using namespace std;" is really for small exemplar programs and isn't really a good recommendation for robust programming of a serious nature. It introduces a lot of symbols; in a large program, you're likely to duplicate some (how many 'max' labels have you seen introduced by the coder). One alternative to always qualifying the label is to introduce just a few commonly used members, such as
using std::cout;
using std::cin;
using std::string;
etc.