distribute	reads
0-500	2903172
500-800	1143899
800-1000	414134
1000-1200	282073
1200-1400	203477
1400-1600	152358
1600-1800	118935
1800-2000	96199
2000-2200	79651
2200-2400	67188
2400-2600	58054
2600-2800	50797
2800-3000	44947
>3000	754522
