0,       const hasher& __hf = hasher(),       const key_equal& __eql = key_equal(),       const allocator_type& __a = allocator_type())       : _M_h(__n, __hf, __eql, __a)       { }        /**        *  @brief  Builds an %unordered_set from a range.        *  @param  __first  An input iterator.        *  @param  __last  An input iterator.        *  @param __n  Minimal initial number of buckets.        *  @param __hf  A hash functor.        *  @param __eql  A key equality functor.        *  @param __a  An allocator object.        *        *  Create an %unordered_set consisting of copies of the elements 