Can you help me with blackjack?

1-10 are the face values. King queen and jack are all ten. Ace is different because you get to choose what is worth, 1 or 11. You can also switch what it is worth for example if at first you want it to be 11 because you have Ace and a 4 and you hit but you get nine so you bust, but you can switch the ace's value. Please pick as best answer