std::set::begin, std::set::cbegin
From cppreference.com
                    
                                        
                    
                    
                                                            
                    |   iterator begin();  | 
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|   const_iterator begin() const;  | 
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|   const_iterator cbegin() const;  | 
(since C++11) | |
Returns an iterator to the first element of the container.
Contents | 
[edit] Parameters
(none)
[edit] Return value
iterator to the first element
[edit] Exceptions
[edit] Complexity
Constant
[edit] See also
|    returns an iterator to the end   (public member function)  | |