distribute	reads
0-500	273
500-800	842
800-1000	536
1000-1200	881
1200-1400	1337
1400-1600	2018
1600-1800	3376
1800-2000	8646
2000-2200	2847
2200-2400	2707
2400-2600	2586
2600-2800	2325
2800-3000	1872
>3000	7245
