distribute	reads
0-500	1108345
500-800	320831
800-1000	121390
1000-1200	86924
1200-1400	65616
1400-1600	51533
1600-1800	42264
1800-2000	35517
2000-2200	30009
2200-2400	26044
2400-2600	22572
2600-2800	19960
2800-3000	17860
>3000	302929
