distribute	reads
0-500	3099893
500-800	1050779
800-1000	392490
1000-1200	274222
1200-1400	202973
1400-1600	154622
1600-1800	123343
1800-2000	100326
2000-2200	83502
2200-2400	70471
2400-2600	60668
2600-2800	52808
2800-3000	46214
>3000	663313
