distribute	reads
0-500	864675
500-800	589370
800-1000	229586
1000-1200	169832
1200-1400	129932
1400-1600	101215
1600-1800	80406
1800-2000	64042
2000-2200	51846
2200-2400	41787
2400-2600	33706
2600-2800	27657
2800-3000	22585
>3000	109936
