Tic Tac Toe Challenge 233

Logic Level 1

X and O are playing tic-tac-toe, and it's now O's turn.

Assuming both are playing optimally, where must O put the mark to draw the match?

Enter your answer as the sum of the numbers in all possible spaces. For example, if you think it's the spaces with 5 or 6, then enter 5 + 6 = 11.