Simple puzzle that challenges your intelligence.

You have a field with numbers and all you need to do is to select numbers to get maximum points. The points are the sum of selected numbers. But one thing, the addition of your numbers continues until a the sum ends up to be a single digit. Eg. you have selected 7 and 8. We add them up and the sum is 15. Next we get the sum of numbers from 15 which is 1 + 5 = 6. We got to a point at which the sum is a single digit. You got 6 points. Get more points than your opponent and you win.