2 4 1 2 1 A 2 4 2 2 1 A B 2 4 3 2 1 A B C 2 4 4 2 1 A B C D 2 4 5 2 1 A B C D E 2 4 6 2 1 A B C D E F 2 4 7 2 1 A B C D E F G 2 4 8 2 1 A B C D E F G H 2 4 9 2 1 A B C D E F G H I 2 4 10 2 1 A B C D E F G H I J