Here are some tests:


10
1
10 + 0 = 10

21
0

43
0

100
3
91 + 9 = 100
95 + 5 = 100
100 + 00 = 100

4444
6
3722 + 722 = 4444
4022 + 422 = 4444
4037 + 407 = 4444
4040 + 404 = 4444
4042 + 402 = 4444
4222 + 222 = 4444

6667
1
6061 + 606 = 6667

6668
6
5834 + 834 = 6668
6034 + 634 = 6668
6059 + 609 = 6668
6062 + 606 = 6668
6064 + 604 = 6668
6334 + 334 = 6668

66667
1
60607 + 6060 = 66667

66668
7
58334 + 8334 = 66668
60334 + 6334 = 66668
60584 + 6084 = 66668
60604 + 6064 = 66668
60608 + 6060 = 66668
60634 + 6034 = 66668
63334 + 3334 = 66668

52525252
11
46262626 + 6262626 = 52525252
47747626 + 4777626 = 52525252
47750126 + 4775126 = 52525252
47750176 + 4775076 = 52525252
47750226 + 4775026 = 52525252
47750231 + 4775021 = 52525252
47752626 + 4772626 = 52525252
47762626 + 4762626 = 52525252
47812626 + 4712626 = 52525252
48262626 + 4262626 = 52525252
51262626 + 1262626 = 52525252

456000
10
378000 + 78000 = 456000
408000 + 48000 = 456000
413000 + 43000 = 456000
414500 + 41500 = 456000
414545 + 41455 = 456000
414546 + 41454 = 456000
414550 + 41450 = 456000
414600 + 41400 = 456000
415000 + 41000 = 456000
428000 + 28000 = 456000

123000321
1
111818474 + 11181847 = 123000321

200020002
16
150010001 + 50010001 = 200020002
181510001 + 18510001 = 200020002
181835001 + 18185001 = 200020002
181836351 + 18183651 = 200020002
181836366 + 18183636 = 200020002
181836371 + 18183631 = 200020002
181836401 + 18183601 = 200020002
181836501 + 18183501 = 200020002
181837001 + 18183001 = 200020002
181840001 + 18180001 = 200020002
181860001 + 18160001 = 200020002
181910001 + 18110001 = 200020002
182010001 + 18010001 = 200020002
185010001 + 15010001 = 200020002
190010001 + 10010001 = 200020002
200010001 + 00010001 = 200020002

1000000000
13
905000000 + 95000000 = 1000000000
909050000 + 90950000 = 1000000000
909090500 + 90909500 = 1000000000
909090905 + 90909095 = 1000000000
909090910 + 90909090 = 1000000000
909090950 + 90909050 = 1000000000
909091000 + 90909000 = 1000000000
909095000 + 90905000 = 1000000000
909100000 + 90900000 = 1000000000
909500000 + 90500000 = 1000000000
910000000 + 90000000 = 1000000000
950000000 + 50000000 = 1000000000
1000000000 + 000000000 = 1000000000