Despite the fact that publically inheriting from standard library containers is considered to be a bad idea, you can "inherit" the constructors:
template <typename T>
struct Set : std::set<T>
{
using std::set<T>::set; // "inherit" the constructors.
};
then
Set<int> s{1,6,4,3,3,9};
Note that a better approach might be to implement functions:
template <typename C>
bool contains(const C& container, const typename C::key_type& key)
{
return container.count(key);
}