distribute	reads
0-500	848218
500-800	417077
800-1000	203096
1000-1200	163952
1200-1400	132564
1400-1600	110475
1600-1800	92351
1800-2000	77946
2000-2200	66387
2200-2400	56821
2400-2600	48522
2600-2800	41849
2800-3000	35797
>3000	206384
