CADDAR
1 2 3 4 1 2 3 4
A A
BX X' B X X'
B C X'
X'
1 2 3 4 X
A A A B B X X'
1 2 3 4 A B C B C
B X'
B X 1 2 3 4
BX X'
X' 1 2 3 4
X'1 2 3 4A B C