std::random_device::max
From cppreference.com
                    
                                        
                    < cpp | numeric | random | random device
                    
                                                            
                    
|   static constexpr result_type max();  | 
(since C++11) | |
Returns the maximum value potentially generated by the random-number engine.
Return value
std::numeric_limits<unsigned int>::max()
Complexity
Constant.
See also
|    [static]  | 
  gets the smallest possible value in the output range  (public static member function)  |