distribute	reads
0-500	1
500-800	1
800-1000	0
1000-1200	5
1200-1400	10
1400-1600	1
1600-1800	20
1800-2000	21
2000-2200	52
2200-2400	109
2400-2600	193
2600-2800	308
2800-3000	428
>3000	20609
