distribute	reads
0-500	3458330
500-800	615603
800-1000	110435
1000-1200	52676
1200-1400	29078
1400-1600	17240
1600-1800	11452
1800-2000	7783
2000-2200	5718
2200-2400	4078
2400-2600	3268
2600-2800	2518
2800-3000	2111
>3000	18285
