vector<int> a(4);
   // Initialize 1, 2, 3, 4
generate(a.begin(), a.end(), SequenceGenerator(1));
while (next_permutation(a.begin(), a.end()))
{
   cout << "Output permutation ";
   vector<int>::iterator p = a.begin();
   while (p != a.end())
   {
      cout << *p << " ";
      ++p;
   }
   cout << "\n";
}