title: Finding the best combination of elements with the max total parameter value
body: <p>I have 100 elements. Each element has 4 features A,B,C,D. Each feature is an integer.</p>
  <p>I want to select 2 elements for each feature, so that I have selected a total of 8 distinct elements. I want to maximize the sum of the 8 selected features A,A,B,B,C,C,D,D.</p>
  <p>A greedy algorithm would be to select the 2 elements with highest A, then the two elements with highest B among the remaining elements, etc. However, this might not be optimal, because the elements that have highest A could also have a much higher B.</p>
  <p>Do we have an algorithm to solve such a problem optimally?</p>