23 Containers library [containers]

23.4 Associative containers [associative]

23.4.5 Class template multimap [multimap] multimap operations [multimap.ops]

iterator find(const key_type &x); const_iterator find(const key_type& x) const; iterator lower_bound(const key_type& x); const_iterator lower_bound(const key_type& x) const; pair<iterator, iterator> equal_range(const key_type& x); pair<const_iterator, const_iterator> equal_range(const key_type& x) const;

The find, lower_bound, upper_bound, and equal_range member functions each have two versions, one const and one non-const. In each case the behavior of the two versions is identical except that the const version returns a const_iterator and the non-const version an iterator ([associative.reqmts]).