C++ Deque max_size()

return_type max_size();

#include <iostream>
#include<deque>
using namespace std;
int main()
{
   deque<int> a={1,2,3,4,5,6};
  cout<<"Maximum size of deque 'a' is:";
  cout<<a.max_size();
  return 0;
}

Maximum size of deque 'a' is:4611686018427387903