1  (IL on line 2, expect nothing)
 2  (DL on line 22, expect nothing)
 3  vvvv  IL on line 5, expected:  A_BC
 4  A
 5  B
 6  C
 7  D
 8  ^^^^
 9  vvvv  DL on line 11, expected:  ACD_
10  A
11  B
12  C
13  D
14  ^^^^
15  vvvv  IL on line 17, expected:  A_
16  A
17  B
18  ^^^^
19  vvvv  IL on line 21, expected:  A_
20  A
21  B
22  ^^^^
23  vvvv  IL on line 24, expected:  _A
24  A

25  B
26  ^^^^
27  vvvv  DL on line 28, expected:  B_
28  A
29  B
30  ^^^^
31
32