distribute	reads
0-500	31
500-800	12
800-1000	5
1000-1200	4
1200-1400	3
1400-1600	7
1600-1800	15
1800-2000	17
2000-2200	15
2200-2400	20
2400-2600	40
2600-2800	58
2800-3000	117
>3000	2837
