distribute	reads
0-500	1
500-800	46
800-1000	63
1000-1200	145
1200-1400	268
1400-1600	502
1600-1800	924
1800-2000	1356
2000-2200	1662
2200-2400	1849
2400-2600	1734
2600-2800	1511
2800-3000	1247
>3000	3044
