distribute	reads
0-500	41
500-800	43
800-1000	27
1000-1200	51
1200-1400	80
1400-1600	114
1600-1800	174
1800-2000	372
2000-2200	565
2200-2400	824
2400-2600	1295
2600-2800	2183
2800-3000	1805
>3000	20934
