1 [M],[M] 2 [],[] 3 [M],[M] 4 [],[] 5 null 6 [M],[M] 7 null 8 [M],[M] 9 null 10 null 11 M 12 null 13 ^ 14 [M],[M] 15 null 16 [M],[M] 17 null 18 null 19 M 20 null 21 ^