distribute	reads
0-500	1836949
500-800	906481
800-1000	353299
1000-1200	251625
1200-1400	186829
1400-1600	144968
1600-1800	113837
1800-2000	92590
2000-2200	77068
2200-2400	65103
2400-2600	55763
2600-2800	48088
2800-3000	41742
>3000	421008
