distribute	reads
0-500	0
500-800	1
800-1000	0
1000-1200	2
1200-1400	4
1400-1600	4
1600-1800	3
1800-2000	9
2000-2200	11
2200-2400	20
2400-2600	31
2600-2800	74
2800-3000	59
>3000	1806
