distribute	reads
0-500	12155947
500-800	5597154
800-1000	2199378
1000-1200	1572558
1200-1400	1172037
1400-1600	901810
1600-1800	717659
1800-2000	582033
2000-2200	484332
2200-2400	405431
2400-2600	344836
2600-2800	297675
2800-3000	257649
>3000	2548052
