distribute	reads
0-500	402214
500-800	196997
800-1000	67452
1000-1200	43737
1200-1400	29135
1400-1600	20416
1600-1800	14738
1800-2000	11020
2000-2200	8486
2200-2400	6775
2400-2600	5439
2600-2800	4527
2800-3000	3692
>3000	38889
