just a few tips :) :
using namespace means you're including std (since u stated std) to be used.
you can also do:
Code
if you're just using cout, which wud be more efficient if you're not using alot of std comands.
Also adding \n (when its in quotes will mean if you cout another message it well be on a new line). There is a different way but i prefer this so it would look like this:
cout << "Hello world! \n";