Time to train - 2

After the gruesome challenge ( PART -1 ) ,Professor McGonagall decides to test Harry with one of her favourite puzzles.

In a party, Minerva and her friends decide to play a party game with cards. There are 20 cards arranged in a row on a table. Each card is showing a positive integer. On each player's turn,he is allowed to take either the left most or right most card. This is done until all the cards are taken. The winner is the player who has the greatest sum of numbers on his/her cards.

What should be Minerva's first move so that she can win the game?

The sequences are:

A - 2 11 13 8 12 5 6 8 9 21 10 7 15 17 18 4 16 18 19 1

B - 12 18 13 4 8 16 17 5 3 19 21 1 6 11 12 18 14 15 6 9