std::random_device::max
From cppreference.com
                    
                                        
                    < cpplrm; | numericlrm; | randomlrm; | random device
                    
                                                            
                    
| static constexpr result_type max(); | (since C++11) | |
Returns the maximum value potentially generated by the random-number engine. This value is equal to std::numeric_limits<unsigned int>::max().
Parameters
(none)
Return value
The maximum potentially generated value.
Complexity
Constant
See also
| [static] | gets the smallest possible value in the output range (public static member function) |