distribute	reads
0-500	123590
500-800	36706
800-1000	8006
1000-1200	3394
1200-1400	1455
1400-1600	686
1600-1800	312
1800-2000	144
2000-2200	82
2200-2400	40
2400-2600	24
2600-2800	16
2800-3000	8
>3000	11
