distribute	reads
0-500	2472356
500-800	1510895
800-1000	696710
1000-1200	559794
1200-1400	465965
1400-1600	395991
1600-1800	341143
1800-2000	299177
2000-2200	262039
2200-2400	230573
2400-2600	202808
2600-2800	179505
2800-3000	157667
>3000	1683378
