4
1 999999997 b
40 300 w
300 634 w
43 47 b

I think the answer is "48 634",why it's "47 634",who can
explain to me?

Thank you!

the integers here is the coordinate, not for numbering the
segment
that mean when they do " 11 28 b", they colored the segment
from (11, 0) to (28, 0) black so that from (28, 0) to (10^9,
0) are still white !

Good luck !

QH@